P1121 info
#1
11-22-2016, 12:31 PM
P1121 info
My car: White 2001 XKR convertible built July 2000 approximately 80,000 miles. On 9-3-16 this happened:
I had spent all day driving about 100 miles and going to 3 different places starting about 6:30AM. Temperature outside was about 90 degrees all day. Parked car in the sun all day so it was hot. Came out of last place about 3PM and drove about 10 miles when the car gave the “no abs etc” and went into fail safe limp home mode. Stopped at side of road several times and shut off engine after a minute or so and restarted. Was still in fail safe limp home mode. Drove slowly about 2 miles and pulled in to a parking lot and shut motor off. Waited about 40 minutes and started it again and still in fail safe mode. Codes at that time were P1111 and P1121. Erased codes and started car but still drove in fail safe mode. Drove car 24 miles home at fail safe speed about 12 MPH (took forever.) Parked in garage. Next day car started up just fine and took scantool computer pictures showing codes P1121 AND P1000.
After doing lots of work on car a year ago it ran fine until 9-13-16. Parked it in garage until now to let me defuse. Have spent the last 40 hours sifting through this forum to collect info about the P1121 code and have collected and edited the following from all the great people who have contributed their knowledge and expertize for our collective benefit. Thank you all. As always I don't know if any of this will work on your car. Use at your own risk.
When the word "I" is used it refers to the original poster not me. There is conflicting
information but I have included all opinions so make your own decisions.
I have not yet implemented any of this info.
Any comments or corrections are gratefully appreciated.
P1121 CODE
The code P0121 is a plug connection issue - maybe. P1121 most of the time a TPS (throttle position sensor) issue on the throttle body but clean all plugs first.
P1121 is the Throttle Position Sensor Circuit Intermittent High Voltage but.....the Jaguar DTC Summary in JTIS says it is the Pedal position sensor misreading between the two circuits.
The TPS (Throttle Position Sensor) will eventually wear out. The PPS (Pedal Position Sensor) is normally trouble free. TPS will usually fail on high mileage cars. We had a low miler at the UK forum who changed his TB to no help. Turned out to be a cheap relay, The Throttle Motor Power Relay.
HARD RESET
Do a hard reset to re-calibrate the TPS.
Remove Negative Battery cable from the Negative Battery Post (10mm Wrench)
- Turn ignition key to on position - this provides a mechanical link to circuits that are isolated
- Turn off ignition
Touch Negative battery cable end to Positive battery cable end and hold there for 30 seconds
(Positive cable will still be connected to Positive Battery Post). When you touch the
negative cable to the positive cable on the battery, there should be nothing at all hooked to the negative terminal. Touching the disconnected negative cable end to the positive cable will short-circuit the supply rails at the ECU's & modules to discharge the internal capacitors. Any electricity stored in the electrical system drains out through the negative cable and into the chassis. The reason to drain the capacitors is THEY still have a complete circuit on the car so you are giving their positive terminal a path to ground to discharge them.
- Turn ignition key to on position
- Turn off ignition
Reconnect Negative Battery cable back to Negative Battery Post
- Start the car
- Let it idle for about 10 Minutes
It is normal after disconnecting the battery that your RPMs will be high when restarting your car and your acceleration will be very brisk. This is part of the ECM learning process and on your next start up it should be at normal levels. This is like doing a full restart and your car will be forced to learn again - you can also temporarily remove stored problem codes this way.
At least it got me out of limp mode (after hard reset AND using my Code reader scan tool to erase fault codes). I was able to drive at normal speeds back to my home.
--------------------
A hard reboot may not clear codes on ODBII. While it MIGHT turn off a check engine light (depending on what the stored codes are) they DO NOT go away. There are codes that will only show when active/pending, and if you shut off the ignition they may not show even with Jaguars IDS (againit depends on the code/situation.)
---------------------------------------
BATTERY
Check all six cells for proper water level. When sitting before starting your battery should be 13.6 volts or better and during running it should be around 14.5. 12 volts is enough for the starter. Battery needs to hold 12.6v overnight.
Look for a parasitic drain on the battery when the car is shut off. The most common one is the little door on the ignition switch where the key goes in. If it hangs up it won't allow the computers to go to sleep mode. Also common is the glove box light and the trunk lights. Set a phone with video ability inside and close the covers and make sure the lights are turning off.
ELECTRIC CONNECTIONS AND CLEANING
Before you unplug anything, remove the cable from the battery negative terminal. When working on anything in the car disconnect the battery. When reconnected after a hard reset the ECM is in a learning state. See HARD RESET.
Electrical connections degrade and lose conductivity over time, and these cars are getting old.
In low mileage cars there is no reason the sensors should be bad. Always start with the cheapest solution. Check the supply of power before repairing or changing your TB. First, look for poor contact in the electrical connectors and in the relay supplying power. A member in our English sister forum changed his TB after a P1121. Failure code returned. P1121 turned out to be a bad TB throttle motor power relay.
Unplug the relays under the hood located near the ECM and plug them back in.
Take your time removing plugs; you do not want to break them in the process of removing them. Carefully unplug TB connectors. Check for off-color. Clean the surface (there are tools, not that expensive, that are specifically made to clean and dress flat and round contacts), spray a good deoxidizer such as Deoxit or contact cleaner on to flush and clean, ensure the contacts are tight, apply a LIGHT coat of dielectric grease, reconnect.
JagRepair.com - Jaguar Repair Information Resource
Clean the plug contacts by hosing them down with contact cleaner, really get them wet, put a rag down so they will drain. Do male and female sides then re-install as above. Your problem might be gone. Happens to me with severe temperature change or heavy fog like moisture.
Clean the MAFS with CRC MAFS cleaner (never touch the internals.) Clean the plug for it, the throttle body plugs, and other plugs with CRC contact cleaner like CRC QD electronic cleaner and use a light coat of Dielectric connector protector. Use a little bulb grease.
Disconnect, clean (as above) and reconnect the following:
IAF Intake Air Temp Sensor
ECT Engine Coolant Temp Sensor
ECU/ECM connecting plugs
On the temp sensor, I had to replace the whole crossover sensor together in March as from age the metal separated from the plastic, not expensive.
If still no luck, remove the ECU/ECM, open it up and inspect it for leaking electrolytic capacitors (signs of wetness, corrosion, or black and brown spots)
You should have removed the negative battery cable fromthe battery – do it!
Unplug all relays and fuses everywhere and reinsert them to clean and re-establish good electrical contact. Swap relays with like relays. If one is bad your problem will probably move to another location code.
GROUND AND OTHER CONNECTIONS
Open the cover to the driver side fuse box at the end of the dashboard. Check the B+ cable is firmly bolted to this fuse box and there is no corrosion. Also re-seat the relay in this fuse box and check and re-seat fuses 14 and 18. Reconnect the battery and see if you still have the problems.
Check the high voltage fuse block behind the spare tire that the positive battery cable runs into; there may be loose connections or corroded fasteners to or from this block, or the metal 'strip' fuses may be corroded or loose.
The schematics show the PPS is grounded through the ECM, clean the EMS bulkhead ground stud and wire terminals.
There may be a ground connection under the computer module passenger side engine compartment. ( US car ) Disconnect the computer (clean those plugs) and check if the ground connection to the body of the car is loose. Clean and torque it down. A member had this problem and the code never came back after 3 years.
A connection at the false bulkhead (fwd. right) has made problems.
There is a ground strap from chassis to gearbox underneath the car at the right side, which is exposed to the elements and tends to degrade.
Member with 1 code problem: A ground problem is entirely possible but I feel it would be throwing a bunch of codes and you are not seeing this. If you want to check the grounds to all points and the engine just pull the fuel pump fuses (keeps the car from starting) and take a lead from the ground terminal on the battery to the front of the engine compartment. Attach a digital volt meter to that lead then the other lead from the volt meter to the engine block. With the volt meter set on 12 volts attempt to start the car at the same time look at the meter and see what you are reading if it is above 0.50 you need to check your ground connections mine was at 0.06.
Battery clamps are thin walled and not very rugged. The wire going from the battery to the high power protection fuses became hot due to poor contact in my car.
NOT SURE OF THIS INFO: We seem to have three sensors; Throttle Pedal Position sensor (TPS), Throttle Blade PositionSensor (TBS) and Mechanical Guard Position Sensor (MGP). These sensors are mostly potentiometers although a Hall sensor was used for one of the sensors in earlier models.
Potentiometers will eventually wear out so in high mileage cars rebuilding the TB with new sensors is probably a good idea.
VEHICLE SPEED CONTROL CABLES
Bulletin Summary: Some vehicles may default to limp home mode because the throttle cable is improperly adjusted. The condition will be accompanied by diagnostic trouble code (dtc) p1121 and/or p1632 being stored in the memory of the engine control mod.
THROTTLE CABLE ADJUSTMENT
Hlgeorge 7-04-2010 #41
How to adjust the 4.0 engine. (Left hand drive)
BRAKE LIGHT SWITCH
Another thing that could be related, the cruise button, leave it off! The brake pedal lights switch located at the top of the brake pedal has 2 microswitches,with cruise on and you press the brake it turns it off in normal behavior, if the microswitch related to this function is faulty then a failsafe trips - so your test is to leave it off and see if it goes into failsafe, if it does again it's pointing at throttle TPS, if not then blasting the switches with contact cleaner or changing the brake switch assembly is the next stage.
THROTTLE BODY
One TB version is vacuum operated (black cylinder next tot he inlet), and the later one is electronic (no black cylinder).
Got the car working again by just flipping the throttle butterfly around a bunch. The sensor is just a potentiometer. I've used old stereos with staticy volume knobs and you can clear up the problem temporarily by just turning the knob around a whole bunch. The problem always comes back.
Have had both issues recently. "restricted performance" .. and "failsafe". A number of years ago -- I had the "failsafe" about 5 times in one month. Back then the codes referenced the TPS on the T-body. Since the car was not used often and the TPS suffers from dirt build up on the contacts -- I tried pushing the throttle to the floor (engine off) to clean the contacts. I did this about 50 times initially ... then about 20 times before I started the car everyday for a week. It went away for a couple of years.
In the TPS there are two parallel traces which are compared continuously, and a difference will throw up a code. (P0121, P0122 or P0123) I find it strange that you don't get any of these codes if it is the TPS.
As for the TPS & PPS on the throttle body they have a redundant system and when one is a little out of sorts (the readings are not equal) a fault will occur resulting in a code P1121 for the PPS & P0121 for the TPS. In the many years of reading throttle body problems I cannot recall one without throwing a code.
Disconnect thebattery cable. The TPS is on the right side of the TB and the PPS is on the left side of the TB. Remove the plugs from the TB and clean the plugs and contacts as stated above, check your engine ground, do a hard reset, clear the codes, and start the car before you remove the TB and sendit to ASI. The P1121 is related to the throttle body so be aware the code may come back.
The major issues were healed by having ASI rebuild my throttle body. P1121 appears to have gone with old Throttle too.
Example 1: You can set the TPS with it on the car, but it is SO much easier off the car. We used the resistance between pins 1 and 3 as the main adjustment, and then checked it with the readings between 1 and 2. As said earlier, we set up the new TB to have almost exactly the same readings as the old TB, and it has worked perfectly since.
I checked the pin resistances on the new throttle body and compared them to the old one. The new throttle body came from ASI fully adjusted counterclockwise, which gave us low readings, especially between pins 1 and 3. We loosened the TPS screws, rotated it until the values were close to what the old unit was showing (which was very close to the values posted here), reinstalled the throttle body, and it works PERFECTLY!
Example 2: I must have advanced the tps when I put it back together. The engine/gearbox fault stopped happening but the shifting changed and so did the idle. Bought an eBay tps and a TS pentalobe bit set. I think its a ts18 or 20 for those security bolts. Changed out the tps. I left the bolts loose and started the car. By adjusting the tps counter clockwise I could actually manipulate the system into triggering the limp mode while idling in my garage. I adjusted it back and took it for a test drive. The incorrect shift points were still there and the car would idle around the neighborhood at 25mph. Pulled back in and adjusted it a bit more clockwise. The idle settled in at about 650-675 rpm. Took it for a ride and it was just like new. I think it is more to do with the tps spring than anything. There was a noticeable difference while fingering the old one compared to the new.
Toyota TPS Sensor Repair Connector Throttle Position Connector Pigtail | eBayr
This looks like the one you need under $30 bucks new, pigtail connector, wiring, and all, don't fit, return it. Worth a try for under $30, but Im told by a Jaguar Salvage Dealer, it is the correct part for us.
- TPS (actually throttle blade position) connector, PI 6, is a black 4-way Sumitomo TS090. May give P 0121.
- Pedal demand/mechanical guard connector, PI 42, is a black 5-way Yazaki 0902. May give P 1121.
- Both these feed to PI 1, a large 57-way connector in a bracket on top of front part of transmission. You can see it down aft of the throttle body. I would be very careful to disconnect, as you may bend the pins on reconnection. But you may try to waggle it.
- Throttle motor connector, PI 33, is a black 2-way twin clip. This is fed from a relay. Malfunction (poor connection) of this relay or its pins (legs), has been mistaken for TB failure.
- There are some differences between AJ26 TB and AJ27 (from VIN 0313039).
Use a Toyota connector part #90980 10711.
We did adjust the TPS based on resistance values to get them very close to the old one. The values are in this thread:
https://www.jaguarforums.com/forum/xk8-xkr-x100-17/tps-replacement-77560/
ASI says that when all else fails, adjust the position of the TB sensor by undoing the two bolts holding it in place just enough to nudge sensor; the holes in the sensor assembly that the bolts go through have a lot of space for adjustment. REPLACE BOLTS WITH ALLEN HEAD SCREWS. I moved the sensor back to where I thought it was before (or maybe .5 mm towards the rear of the car) and tightened the screws again. The car started fine but the RPM stayed the same at ~1200-1500. As I was contemplating giving up, I reset the sensors one last time by removing the battery like I mentioned before. Started the engine. RPM 600-650 for the first time in a month.
The throttle cable needed to be loosened from what it was set to on the old TB.
The TPS screws are a 5 point security bit #20, not Jaguar specific. You can get a whole set on ebay for 4$!
Here is the current ATE (ASI) EBAY listing for 1999 thru 2003 Jaguar XJR Throttle Body Rebuild service - $239.00 - nice low price
(I paid $326 in August 2012 for ASI Ebay same service 2001 XJ8):
99 00 01 02 03 Jaguar XKR XJR Throttle Body Repair ServiceSuper Charged | eBay
ASI usually has a much lower price when they put the rebuild service on EBAY than they do on their own ASI website ($239 versus $489).
THROTTLE POSITIONSENSOR (TPS) MISMATCHED MATERIALS
Do you know if an upgrade was done on the TPS leads to the throttle body (TB)?
http://jagrepair.com/images/TSB/XK8/303-58.pdf
LOOK FOR MISMATCHED CONNECTOR MATERIALS –GOLD TERMINALS ON THE TPS AND TIN TERMINALS ON THE WIRING HARNESS
4 EACH OF GOLD TERMINATED CABLE PART #LNG 3956AA
1 OF CONVOLUTED TUBE PART #LST 6754AA
SNG Barratt - The Ultimate Jaguar Parts Specialist
LnG3956AA. - I placed an order with Nalley Jaguar (listprice is $17.50 each). Nalley gives us forum members a 25% discount and freeshipping (total cost for 4 parts is $52.50).
Following my rebuild I had a persistent P1121 and only a replacement throttle fixed it. Depending on mileage, the higher it is the more likely you'll require another TB, but it's worth exchanging the plug pins because whatever they cost its cheaper than a TB - and if it turns out to be the TB, at least you have it updated ready for the replacement TB.
I have had great success in using the proper size end to end crimp connectors with heat shrink material over the top using a heat gun.
If the TPS plug is cracked (or if you don't want to shell out for the gold connectors), there is a Toyota part that works. I did the gold connectors first, but the plug itself was in too bad of shape, I ended up splicing in the Toyota part (with the intention of replacing the contacts with gold ones), but ended up just leaving the stock Toyota part. I also had a rebuilt TPS to go with it, and my problems were cured.
Here is the part info:
Designed Fitment: Toyota or Geo Prizm
Brand:Standard Motor Products
Manufacturer Part Number:RPCTH151
Interchange Part Number:213-446, 213930
Other Part Number:89452-33010, 94853125
Other Part Numbers:1985003011, 89452-06010, 89452-12050, 89452-22090
FUEL PUMP AND FUEL
I finally diagnosed exactly the same problem, RPM drop when pushed gas pedal. My scanner showed fuel pressure drop. I checked voltage going to fuel pump, it was increasing as it should, so it was definitely fuel pump problem (or dirty fuel filter or screen).
As stated above you may want to check the fuel pressure regulator, I've seen a number of posts from early XK that had bad ones. Or check fuel pressure with a gauge from schrader valve.
I still want to get the gas gauge down to the red mark, put in another bottle of Techron, fill it up and take it for a drive. Hope this will clean out the injection system out for a while.
I ran 2 tanks of fresh fuel each with Techron and the codes left. I actually made it with ease from New York to Florida and more.
Running Techron in my fuel tank did clear bank 2 running rich but now instead of code PO175 for Bank 2, Now I am getting PO172 which is Bank 1 running rich. Also going in and out of restricted mode with check engine light on.
MASS AIR FUEL(MAF) SENSOR
Replaced the MAF sensor with a rebuilt one from advanced auto. The replacement sensor had the exact same form factor as OEM but it had different looking filaments and also only 2 filaments instead of 3 like the OEM MAF sensor. It also had 2 fewer pins on the connector than the OEM sensor. I noticed that the cable leading to the OEM sensor had 2 fewer conductors than the OEM sensor itself so it seems that missing that third filament doesn't matter anyway.
That solved the problem. I started the car about 10 times to test it and it had no problems.
The poster advised to check on the connection of the MAF connectors, especially the pins. My connector showed perfectly clean, and I was already a bit disappointed. Nevertheless, I bent the pins just a little bit down to have some better contact pressure. Guess what; Long term Fuel Trims dropped from -15 back to ~-5 at warm idle for both banks, and the MAF reading itself dropped just below the factory advised value for idle.
EGR VALVE
EGR bolts have a history of coming loose. Use some locktite on them. I worked on a XKR a couple of years ago that had the same problem, and others have mentioned it.
If the EGR valve is operating properly, it seems like you should be able to repair it. Since the EGR valve passes exhaust gasses at pretty high temperatures, silicone sealant may not be able to maintain the integrity of its bond. Even the Permatex high-temp red RTV is only rated to 600F continuous, which is not much higher than the O2 sensor heaters reach just to get the sensors operating properly. J.B. Weld High Heat epoxy is only rated to 550F and only 400F continuous.
I repaired the EGR pipe fitting on one of the exhaust manifolds of our '93 using Blue Magic ThermoSteel and it's held for more than 10 years. It's goodfor up to 2400F:
VACUUM LEAKS
Pull up the dip stick. If there is a leak there is no change in engine.
MISCELLANEOUS
New Jaguar 02 04 x Type Denso Throttle Position Sensor 1985003300 | eBay
Jaguar XJ8 XK8 4 0L Throttle Position Sensor DENSO198500 3250 |eBay
http://www.tomco-inc.com/Catalog/tps%20sensors.pdf
I'm going to call Brock LR on monday....if they cansupply a TPS for a RR Sport SC at right money, I'll buy and bolt it on for atest, although this option would benefit 4.2 owners I guess (Denso 3300) Itmight be better to test on an XK/XKR X350/358 and later S Types...personallyfeel the denso 3250 and 3300 are close enough to swap, just hope it works...
I had luck calling Jagbits.com and Motorcarsltd.com forused plugs but they will cost you.
I had spent all day driving about 100 miles and going to 3 different places starting about 6:30AM. Temperature outside was about 90 degrees all day. Parked car in the sun all day so it was hot. Came out of last place about 3PM and drove about 10 miles when the car gave the “no abs etc” and went into fail safe limp home mode. Stopped at side of road several times and shut off engine after a minute or so and restarted. Was still in fail safe limp home mode. Drove slowly about 2 miles and pulled in to a parking lot and shut motor off. Waited about 40 minutes and started it again and still in fail safe mode. Codes at that time were P1111 and P1121. Erased codes and started car but still drove in fail safe mode. Drove car 24 miles home at fail safe speed about 12 MPH (took forever.) Parked in garage. Next day car started up just fine and took scantool computer pictures showing codes P1121 AND P1000.
After doing lots of work on car a year ago it ran fine until 9-13-16. Parked it in garage until now to let me defuse. Have spent the last 40 hours sifting through this forum to collect info about the P1121 code and have collected and edited the following from all the great people who have contributed their knowledge and expertize for our collective benefit. Thank you all. As always I don't know if any of this will work on your car. Use at your own risk.
When the word "I" is used it refers to the original poster not me. There is conflicting
information but I have included all opinions so make your own decisions.
I have not yet implemented any of this info.
Any comments or corrections are gratefully appreciated.
P1121 CODE
The code P0121 is a plug connection issue - maybe. P1121 most of the time a TPS (throttle position sensor) issue on the throttle body but clean all plugs first.
P1121 is the Throttle Position Sensor Circuit Intermittent High Voltage but.....the Jaguar DTC Summary in JTIS says it is the Pedal position sensor misreading between the two circuits.
The TPS (Throttle Position Sensor) will eventually wear out. The PPS (Pedal Position Sensor) is normally trouble free. TPS will usually fail on high mileage cars. We had a low miler at the UK forum who changed his TB to no help. Turned out to be a cheap relay, The Throttle Motor Power Relay.
HARD RESET
Do a hard reset to re-calibrate the TPS.
Remove Negative Battery cable from the Negative Battery Post (10mm Wrench)
- Turn ignition key to on position - this provides a mechanical link to circuits that are isolated
- Turn off ignition
Touch Negative battery cable end to Positive battery cable end and hold there for 30 seconds
(Positive cable will still be connected to Positive Battery Post). When you touch the
negative cable to the positive cable on the battery, there should be nothing at all hooked to the negative terminal. Touching the disconnected negative cable end to the positive cable will short-circuit the supply rails at the ECU's & modules to discharge the internal capacitors. Any electricity stored in the electrical system drains out through the negative cable and into the chassis. The reason to drain the capacitors is THEY still have a complete circuit on the car so you are giving their positive terminal a path to ground to discharge them.
- Turn ignition key to on position
- Turn off ignition
Reconnect Negative Battery cable back to Negative Battery Post
- Start the car
- Let it idle for about 10 Minutes
It is normal after disconnecting the battery that your RPMs will be high when restarting your car and your acceleration will be very brisk. This is part of the ECM learning process and on your next start up it should be at normal levels. This is like doing a full restart and your car will be forced to learn again - you can also temporarily remove stored problem codes this way.
At least it got me out of limp mode (after hard reset AND using my Code reader scan tool to erase fault codes). I was able to drive at normal speeds back to my home.
--------------------
A hard reboot may not clear codes on ODBII. While it MIGHT turn off a check engine light (depending on what the stored codes are) they DO NOT go away. There are codes that will only show when active/pending, and if you shut off the ignition they may not show even with Jaguars IDS (againit depends on the code/situation.)
---------------------------------------
BATTERY
Check all six cells for proper water level. When sitting before starting your battery should be 13.6 volts or better and during running it should be around 14.5. 12 volts is enough for the starter. Battery needs to hold 12.6v overnight.
Look for a parasitic drain on the battery when the car is shut off. The most common one is the little door on the ignition switch where the key goes in. If it hangs up it won't allow the computers to go to sleep mode. Also common is the glove box light and the trunk lights. Set a phone with video ability inside and close the covers and make sure the lights are turning off.
ELECTRIC CONNECTIONS AND CLEANING
Before you unplug anything, remove the cable from the battery negative terminal. When working on anything in the car disconnect the battery. When reconnected after a hard reset the ECM is in a learning state. See HARD RESET.
Electrical connections degrade and lose conductivity over time, and these cars are getting old.
In low mileage cars there is no reason the sensors should be bad. Always start with the cheapest solution. Check the supply of power before repairing or changing your TB. First, look for poor contact in the electrical connectors and in the relay supplying power. A member in our English sister forum changed his TB after a P1121. Failure code returned. P1121 turned out to be a bad TB throttle motor power relay.
Unplug the relays under the hood located near the ECM and plug them back in.
Take your time removing plugs; you do not want to break them in the process of removing them. Carefully unplug TB connectors. Check for off-color. Clean the surface (there are tools, not that expensive, that are specifically made to clean and dress flat and round contacts), spray a good deoxidizer such as Deoxit or contact cleaner on to flush and clean, ensure the contacts are tight, apply a LIGHT coat of dielectric grease, reconnect.
JagRepair.com - Jaguar Repair Information Resource
Clean the plug contacts by hosing them down with contact cleaner, really get them wet, put a rag down so they will drain. Do male and female sides then re-install as above. Your problem might be gone. Happens to me with severe temperature change or heavy fog like moisture.
Clean the MAFS with CRC MAFS cleaner (never touch the internals.) Clean the plug for it, the throttle body plugs, and other plugs with CRC contact cleaner like CRC QD electronic cleaner and use a light coat of Dielectric connector protector. Use a little bulb grease.
Disconnect, clean (as above) and reconnect the following:
IAF Intake Air Temp Sensor
ECT Engine Coolant Temp Sensor
ECU/ECM connecting plugs
On the temp sensor, I had to replace the whole crossover sensor together in March as from age the metal separated from the plastic, not expensive.
If still no luck, remove the ECU/ECM, open it up and inspect it for leaking electrolytic capacitors (signs of wetness, corrosion, or black and brown spots)
You should have removed the negative battery cable fromthe battery – do it!
Unplug all relays and fuses everywhere and reinsert them to clean and re-establish good electrical contact. Swap relays with like relays. If one is bad your problem will probably move to another location code.
GROUND AND OTHER CONNECTIONS
Open the cover to the driver side fuse box at the end of the dashboard. Check the B+ cable is firmly bolted to this fuse box and there is no corrosion. Also re-seat the relay in this fuse box and check and re-seat fuses 14 and 18. Reconnect the battery and see if you still have the problems.
Check the high voltage fuse block behind the spare tire that the positive battery cable runs into; there may be loose connections or corroded fasteners to or from this block, or the metal 'strip' fuses may be corroded or loose.
The schematics show the PPS is grounded through the ECM, clean the EMS bulkhead ground stud and wire terminals.
There may be a ground connection under the computer module passenger side engine compartment. ( US car ) Disconnect the computer (clean those plugs) and check if the ground connection to the body of the car is loose. Clean and torque it down. A member had this problem and the code never came back after 3 years.
A connection at the false bulkhead (fwd. right) has made problems.
There is a ground strap from chassis to gearbox underneath the car at the right side, which is exposed to the elements and tends to degrade.
Member with 1 code problem: A ground problem is entirely possible but I feel it would be throwing a bunch of codes and you are not seeing this. If you want to check the grounds to all points and the engine just pull the fuel pump fuses (keeps the car from starting) and take a lead from the ground terminal on the battery to the front of the engine compartment. Attach a digital volt meter to that lead then the other lead from the volt meter to the engine block. With the volt meter set on 12 volts attempt to start the car at the same time look at the meter and see what you are reading if it is above 0.50 you need to check your ground connections mine was at 0.06.
Battery clamps are thin walled and not very rugged. The wire going from the battery to the high power protection fuses became hot due to poor contact in my car.
NOT SURE OF THIS INFO: We seem to have three sensors; Throttle Pedal Position sensor (TPS), Throttle Blade PositionSensor (TBS) and Mechanical Guard Position Sensor (MGP). These sensors are mostly potentiometers although a Hall sensor was used for one of the sensors in earlier models.
Potentiometers will eventually wear out so in high mileage cars rebuilding the TB with new sensors is probably a good idea.
VEHICLE SPEED CONTROL CABLES
Bulletin Summary: Some vehicles may default to limp home mode because the throttle cable is improperly adjusted. The condition will be accompanied by diagnostic trouble code (dtc) p1121 and/or p1632 being stored in the memory of the engine control mod.
THROTTLE CABLE ADJUSTMENT
Hlgeorge 7-04-2010 #41
How to adjust the 4.0 engine. (Left hand drive)
BRAKE LIGHT SWITCH
Another thing that could be related, the cruise button, leave it off! The brake pedal lights switch located at the top of the brake pedal has 2 microswitches,with cruise on and you press the brake it turns it off in normal behavior, if the microswitch related to this function is faulty then a failsafe trips - so your test is to leave it off and see if it goes into failsafe, if it does again it's pointing at throttle TPS, if not then blasting the switches with contact cleaner or changing the brake switch assembly is the next stage.
THROTTLE BODY
One TB version is vacuum operated (black cylinder next tot he inlet), and the later one is electronic (no black cylinder).
Got the car working again by just flipping the throttle butterfly around a bunch. The sensor is just a potentiometer. I've used old stereos with staticy volume knobs and you can clear up the problem temporarily by just turning the knob around a whole bunch. The problem always comes back.
Have had both issues recently. "restricted performance" .. and "failsafe". A number of years ago -- I had the "failsafe" about 5 times in one month. Back then the codes referenced the TPS on the T-body. Since the car was not used often and the TPS suffers from dirt build up on the contacts -- I tried pushing the throttle to the floor (engine off) to clean the contacts. I did this about 50 times initially ... then about 20 times before I started the car everyday for a week. It went away for a couple of years.
In the TPS there are two parallel traces which are compared continuously, and a difference will throw up a code. (P0121, P0122 or P0123) I find it strange that you don't get any of these codes if it is the TPS.
As for the TPS & PPS on the throttle body they have a redundant system and when one is a little out of sorts (the readings are not equal) a fault will occur resulting in a code P1121 for the PPS & P0121 for the TPS. In the many years of reading throttle body problems I cannot recall one without throwing a code.
Disconnect thebattery cable. The TPS is on the right side of the TB and the PPS is on the left side of the TB. Remove the plugs from the TB and clean the plugs and contacts as stated above, check your engine ground, do a hard reset, clear the codes, and start the car before you remove the TB and sendit to ASI. The P1121 is related to the throttle body so be aware the code may come back.
The major issues were healed by having ASI rebuild my throttle body. P1121 appears to have gone with old Throttle too.
Example 1: You can set the TPS with it on the car, but it is SO much easier off the car. We used the resistance between pins 1 and 3 as the main adjustment, and then checked it with the readings between 1 and 2. As said earlier, we set up the new TB to have almost exactly the same readings as the old TB, and it has worked perfectly since.
I checked the pin resistances on the new throttle body and compared them to the old one. The new throttle body came from ASI fully adjusted counterclockwise, which gave us low readings, especially between pins 1 and 3. We loosened the TPS screws, rotated it until the values were close to what the old unit was showing (which was very close to the values posted here), reinstalled the throttle body, and it works PERFECTLY!
Example 2: I must have advanced the tps when I put it back together. The engine/gearbox fault stopped happening but the shifting changed and so did the idle. Bought an eBay tps and a TS pentalobe bit set. I think its a ts18 or 20 for those security bolts. Changed out the tps. I left the bolts loose and started the car. By adjusting the tps counter clockwise I could actually manipulate the system into triggering the limp mode while idling in my garage. I adjusted it back and took it for a test drive. The incorrect shift points were still there and the car would idle around the neighborhood at 25mph. Pulled back in and adjusted it a bit more clockwise. The idle settled in at about 650-675 rpm. Took it for a ride and it was just like new. I think it is more to do with the tps spring than anything. There was a noticeable difference while fingering the old one compared to the new.
Toyota TPS Sensor Repair Connector Throttle Position Connector Pigtail | eBayr
This looks like the one you need under $30 bucks new, pigtail connector, wiring, and all, don't fit, return it. Worth a try for under $30, but Im told by a Jaguar Salvage Dealer, it is the correct part for us.
- TPS (actually throttle blade position) connector, PI 6, is a black 4-way Sumitomo TS090. May give P 0121.
- Pedal demand/mechanical guard connector, PI 42, is a black 5-way Yazaki 0902. May give P 1121.
- Both these feed to PI 1, a large 57-way connector in a bracket on top of front part of transmission. You can see it down aft of the throttle body. I would be very careful to disconnect, as you may bend the pins on reconnection. But you may try to waggle it.
- Throttle motor connector, PI 33, is a black 2-way twin clip. This is fed from a relay. Malfunction (poor connection) of this relay or its pins (legs), has been mistaken for TB failure.
- There are some differences between AJ26 TB and AJ27 (from VIN 0313039).
Use a Toyota connector part #90980 10711.
We did adjust the TPS based on resistance values to get them very close to the old one. The values are in this thread:
https://www.jaguarforums.com/forum/xk8-xkr-x100-17/tps-replacement-77560/
ASI says that when all else fails, adjust the position of the TB sensor by undoing the two bolts holding it in place just enough to nudge sensor; the holes in the sensor assembly that the bolts go through have a lot of space for adjustment. REPLACE BOLTS WITH ALLEN HEAD SCREWS. I moved the sensor back to where I thought it was before (or maybe .5 mm towards the rear of the car) and tightened the screws again. The car started fine but the RPM stayed the same at ~1200-1500. As I was contemplating giving up, I reset the sensors one last time by removing the battery like I mentioned before. Started the engine. RPM 600-650 for the first time in a month.
The throttle cable needed to be loosened from what it was set to on the old TB.
The TPS screws are a 5 point security bit #20, not Jaguar specific. You can get a whole set on ebay for 4$!
Here is the current ATE (ASI) EBAY listing for 1999 thru 2003 Jaguar XJR Throttle Body Rebuild service - $239.00 - nice low price
(I paid $326 in August 2012 for ASI Ebay same service 2001 XJ8):
99 00 01 02 03 Jaguar XKR XJR Throttle Body Repair ServiceSuper Charged | eBay
ASI usually has a much lower price when they put the rebuild service on EBAY than they do on their own ASI website ($239 versus $489).
THROTTLE POSITIONSENSOR (TPS) MISMATCHED MATERIALS
Do you know if an upgrade was done on the TPS leads to the throttle body (TB)?
http://jagrepair.com/images/TSB/XK8/303-58.pdf
LOOK FOR MISMATCHED CONNECTOR MATERIALS –GOLD TERMINALS ON THE TPS AND TIN TERMINALS ON THE WIRING HARNESS
4 EACH OF GOLD TERMINATED CABLE PART #LNG 3956AA
1 OF CONVOLUTED TUBE PART #LST 6754AA
SNG Barratt - The Ultimate Jaguar Parts Specialist
LnG3956AA. - I placed an order with Nalley Jaguar (listprice is $17.50 each). Nalley gives us forum members a 25% discount and freeshipping (total cost for 4 parts is $52.50).
Following my rebuild I had a persistent P1121 and only a replacement throttle fixed it. Depending on mileage, the higher it is the more likely you'll require another TB, but it's worth exchanging the plug pins because whatever they cost its cheaper than a TB - and if it turns out to be the TB, at least you have it updated ready for the replacement TB.
I have had great success in using the proper size end to end crimp connectors with heat shrink material over the top using a heat gun.
If the TPS plug is cracked (or if you don't want to shell out for the gold connectors), there is a Toyota part that works. I did the gold connectors first, but the plug itself was in too bad of shape, I ended up splicing in the Toyota part (with the intention of replacing the contacts with gold ones), but ended up just leaving the stock Toyota part. I also had a rebuilt TPS to go with it, and my problems were cured.
Here is the part info:
Designed Fitment: Toyota or Geo Prizm
Brand:Standard Motor Products
Manufacturer Part Number:RPCTH151
Interchange Part Number:213-446, 213930
Other Part Number:89452-33010, 94853125
Other Part Numbers:1985003011, 89452-06010, 89452-12050, 89452-22090
FUEL PUMP AND FUEL
I finally diagnosed exactly the same problem, RPM drop when pushed gas pedal. My scanner showed fuel pressure drop. I checked voltage going to fuel pump, it was increasing as it should, so it was definitely fuel pump problem (or dirty fuel filter or screen).
As stated above you may want to check the fuel pressure regulator, I've seen a number of posts from early XK that had bad ones. Or check fuel pressure with a gauge from schrader valve.
I still want to get the gas gauge down to the red mark, put in another bottle of Techron, fill it up and take it for a drive. Hope this will clean out the injection system out for a while.
I ran 2 tanks of fresh fuel each with Techron and the codes left. I actually made it with ease from New York to Florida and more.
Running Techron in my fuel tank did clear bank 2 running rich but now instead of code PO175 for Bank 2, Now I am getting PO172 which is Bank 1 running rich. Also going in and out of restricted mode with check engine light on.
MASS AIR FUEL(MAF) SENSOR
Replaced the MAF sensor with a rebuilt one from advanced auto. The replacement sensor had the exact same form factor as OEM but it had different looking filaments and also only 2 filaments instead of 3 like the OEM MAF sensor. It also had 2 fewer pins on the connector than the OEM sensor. I noticed that the cable leading to the OEM sensor had 2 fewer conductors than the OEM sensor itself so it seems that missing that third filament doesn't matter anyway.
That solved the problem. I started the car about 10 times to test it and it had no problems.
The poster advised to check on the connection of the MAF connectors, especially the pins. My connector showed perfectly clean, and I was already a bit disappointed. Nevertheless, I bent the pins just a little bit down to have some better contact pressure. Guess what; Long term Fuel Trims dropped from -15 back to ~-5 at warm idle for both banks, and the MAF reading itself dropped just below the factory advised value for idle.
EGR VALVE
EGR bolts have a history of coming loose. Use some locktite on them. I worked on a XKR a couple of years ago that had the same problem, and others have mentioned it.
If the EGR valve is operating properly, it seems like you should be able to repair it. Since the EGR valve passes exhaust gasses at pretty high temperatures, silicone sealant may not be able to maintain the integrity of its bond. Even the Permatex high-temp red RTV is only rated to 600F continuous, which is not much higher than the O2 sensor heaters reach just to get the sensors operating properly. J.B. Weld High Heat epoxy is only rated to 550F and only 400F continuous.
I repaired the EGR pipe fitting on one of the exhaust manifolds of our '93 using Blue Magic ThermoSteel and it's held for more than 10 years. It's goodfor up to 2400F:
VACUUM LEAKS
Pull up the dip stick. If there is a leak there is no change in engine.
MISCELLANEOUS
Jaguar XJ8 XK8 4 0L Throttle Position Sensor DENSO198500 3250 |eBay
http://www.tomco-inc.com/Catalog/tps%20sensors.pdf
I'm going to call Brock LR on monday....if they cansupply a TPS for a RR Sport SC at right money, I'll buy and bolt it on for atest, although this option would benefit 4.2 owners I guess (Denso 3300) Itmight be better to test on an XK/XKR X350/358 and later S Types...personallyfeel the denso 3250 and 3300 are close enough to swap, just hope it works...
I had luck calling Jagbits.com and Motorcarsltd.com forused plugs but they will cost you.
The following 9 users liked this post by Poet:
cjd777 (11-24-2016),
GordoCatCar (11-26-2016),
grantorino62 (11-23-2016),
IowaPopPop (11-26-2016),
just_byron (05-27-2018),
and 4 others liked this post.
#3
11-22-2016, 04:48 PM
I think I said at the beginning it was a compilation of information for anyone who has a P1121 problem. This forum has helped me a lot and I felt that I could help others and save them a lot of time looking for info about a P1121 code by trying to present it all in one package instead of having to search it all out.
#7
11-24-2016, 05:49 AM
Senior Member
Trending Topics
#9
02-04-2018, 04:32 PM
Member
My 2004 Jaguar X-type 2.5 has trottle body sensor (TPS) : Denso 198500-3300.
Here I info that TBS of several modela of Toyota has compatibile TPS as Denso 198500-3300.
If YES, please for informarion which model of Toyota has that sensor, or which number factory product is? Maybe also Denso, but number I need.
There is no Jaguar service in my country, but there is oficial Toyota service and they have parts.
Here I info that TBS of several modela of Toyota has compatibile TPS as Denso 198500-3300.
If YES, please for informarion which model of Toyota has that sensor, or which number factory product is? Maybe also Denso, but number I need.
There is no Jaguar service in my country, but there is oficial Toyota service and they have parts.
#10
03-14-2018, 04:03 PM
TPS Fix (I Hope!)
Hey folks, there's a lot of good advice on this thread, except none of it worked for me. When I faced the prospect of having to shell out $$$ for a whole new throttle body, I got brave, took a chance, and it seems to have worked. Sooo, if all else fails, try this:
Disconnect the battery.
MARK THE POSITION OF THE TPS ON THE THROTTLE BODY SO YOU CAN REPLACE IT WITH THE SAME ORIENTATION.
Remove the TPS from the throttle body. I didn't have a 5-point driver, so I found it easier to just remove the whole throttle assembly. That's not to tough once you figure out how to remove those funky hose clips. Then I removed the TPS screws with needle-nosed vice-grips. Buggered them up a bit, but I was going to replace them with stainless Allen-head screws anyway.
Grab your trusty can of CRC contact cleaner.
OK, here's the tricky part. Using a drill bit just slightly larger than the long, plastic, CRC squirter extension thingy, drill a hole near the top of each side of the TPS case. Be EXTRA CAREFUL to NOT drill any deeper than just getting through the shell because there are wires and other things in there. Damage any of that stuff and all bets are off.
Now, stick the aforementioned squirter thingy into one of the holes and, while holding the TPS vertically, fill that puppy with contact cleaner until it flows out the other hole. Work the potentiometer wiper mechanism through its rotation several times and drain the unit as best you can. I thought of blowing it out with compressed air, but chose not to take the chance on disturbing anything inside. I just let it dry out for a couple days then sealed the holes with epoxy.
Put it all back together with the TPS positioned right where it was originally.
I then followed the re-connection/programming procedure published by member "Redline" in the following thread:
https://www.jaguarforums.com/forum/x...amming-193213/ (Thanks, Redline.)
She runs like new. Don't know if it will last, but she was going into limp mode about 5 times a day and I am now at 3 days without incident.
Cheers -
Disconnect the battery.
MARK THE POSITION OF THE TPS ON THE THROTTLE BODY SO YOU CAN REPLACE IT WITH THE SAME ORIENTATION.
Remove the TPS from the throttle body. I didn't have a 5-point driver, so I found it easier to just remove the whole throttle assembly. That's not to tough once you figure out how to remove those funky hose clips. Then I removed the TPS screws with needle-nosed vice-grips. Buggered them up a bit, but I was going to replace them with stainless Allen-head screws anyway.
Grab your trusty can of CRC contact cleaner.
OK, here's the tricky part. Using a drill bit just slightly larger than the long, plastic, CRC squirter extension thingy, drill a hole near the top of each side of the TPS case. Be EXTRA CAREFUL to NOT drill any deeper than just getting through the shell because there are wires and other things in there. Damage any of that stuff and all bets are off.
Now, stick the aforementioned squirter thingy into one of the holes and, while holding the TPS vertically, fill that puppy with contact cleaner until it flows out the other hole. Work the potentiometer wiper mechanism through its rotation several times and drain the unit as best you can. I thought of blowing it out with compressed air, but chose not to take the chance on disturbing anything inside. I just let it dry out for a couple days then sealed the holes with epoxy.
Put it all back together with the TPS positioned right where it was originally.
I then followed the re-connection/programming procedure published by member "Redline" in the following thread:
https://www.jaguarforums.com/forum/x...amming-193213/ (Thanks, Redline.)
She runs like new. Don't know if it will last, but she was going into limp mode about 5 times a day and I am now at 3 days without incident.
Cheers -
#11
03-14-2018, 04:36 PM
Senior Member
'Hey folks, there's a lot of good advice on this thread, except none of it worked for me.'
Now theres a surprise! It was just a load of cut and paste articles off the internet in no real logical order. Your best bet would have been to follow the Jaguar flow chart found on Jaguarepair.com. All checks done in a logical and thorough order that lead you to the real issue very quickly as you would expect as its written by the factory.
http://www.jagrepair.com/images/TSB/...Flowcharts.pdf
Now theres a surprise! It was just a load of cut and paste articles off the internet in no real logical order. Your best bet would have been to follow the Jaguar flow chart found on Jaguarepair.com. All checks done in a logical and thorough order that lead you to the real issue very quickly as you would expect as its written by the factory.
http://www.jagrepair.com/images/TSB/...Flowcharts.pdf
The following users liked this post:
Gus (03-14-2018)
#12
03-14-2018, 04:51 PM
Veteran Member
I am a little confused. The P1121 is for Pedal Position Sensor and the P0121 is for Throttle Position Sensor. My experience has been that the code does follow the sensor and I experienced both issues.
Link to P0121 TSB http://jagrepair.com/images/TSB/XK8/303-58.pdf
Link to codes http://jagrepair.com/images/AutoRepa...J27%201999.pdf
Link to P0121 TSB http://jagrepair.com/images/TSB/XK8/303-58.pdf
Link to codes http://jagrepair.com/images/AutoRepa...J27%201999.pdf
#13
03-15-2018, 01:48 PM
Nice fix
I Too experienced the dreaded TPS fault a year ago, random and often shut downs made me want to do bodily harm to some engineer, its not the cars fault.
I found a new Denso TPS on Ebay for under $10, but couldn't get it to work DISPITE following every ones ideas after I followed the JTIS to the letter, more than once.
So I tried the old one, sprayed contact cleaner into the crevices and a small hole in the TPS, it dripped out brown, put it back on and its been fine for over a year now, I believe there is a firmware glitch in this system, a new identical TPS should work, its a dual "pot", not hi tech.
I bet your fix works, just my two cents...
I found a new Denso TPS on Ebay for under $10, but couldn't get it to work DISPITE following every ones ideas after I followed the JTIS to the letter, more than once.
So I tried the old one, sprayed contact cleaner into the crevices and a small hole in the TPS, it dripped out brown, put it back on and its been fine for over a year now, I believe there is a firmware glitch in this system, a new identical TPS should work, its a dual "pot", not hi tech.
I bet your fix works, just my two cents...
#14
03-16-2018, 01:02 PM
'Hey folks, there's a lot of good advice on this thread, except none of it worked for me.'
Now theres a surprise! It was just a load of cut and paste articles off the internet in no real logical order. Your best bet would have been to follow the Jaguar flow chart found on Jaguarepair.com. All checks done in a logical and thorough order that lead you to the real issue very quickly as you would expect as its written by the factory.
http://www.jagrepair.com/images/TSB/...Flowcharts.pdf
Now theres a surprise! It was just a load of cut and paste articles off the internet in no real logical order. Your best bet would have been to follow the Jaguar flow chart found on Jaguarepair.com. All checks done in a logical and thorough order that lead you to the real issue very quickly as you would expect as its written by the factory.
http://www.jagrepair.com/images/TSB/...Flowcharts.pdf
Cheers,
#15
03-16-2018, 03:51 PM
Veteran Member
Yes you are correct the Throttle Body is a bit costly but you can send it to ASI and have it tested and repaired at a fraction of the price of a new one.
Link http://www.autoecu.com/index.php?p=1
Link http://www.autoecu.com/index.php?p=1
The following users liked this post:
XK8+XJ8L (03-18-2018)
#16
03-18-2018, 01:34 AM
Yes you are correct the Throttle Body is a bit costly but you can send it to ASI and have it tested and repaired at a fraction of the price of a new one.
Link http://www.autoecu.com/index.php?p=1
Link http://www.autoecu.com/index.php?p=1
#17
03-20-2018, 12:01 PM
Veteran Member
