Hi Flay
The diagnostics that you listed are for AJ26 (1998 - Early 1999) Engine - ECM connector EM11 - not your model year.

Here is the AJ26 ECM connectors pinouts (click on the image after the dropbox.com webpage opens to get a sharper view) :

https://www.dropbox.com/s/mdgvpb0p5h...%20pinouts.JPG


Here is the diagnostics for AJ27 (Late 1999-2003) Engine - ECM connector EM81 Also TP sensor connector PI06 (it is PI6 on Wiring Guide Diagrams)

PINPOINT TEST D : DTC P0121, P0122, P0123; THROTTLE POSITION (TP) SENSOR RANGE/PERFORMANCE, HIGH/LOW VOLTAGE
TEST CONDITIONS
DETAILS/RESULTS/ACTIONS
D1: CHECK THE TP SENSOR SENSE CIRCUIT FOR HIGH RESISTANCE
1 Disconnect the battery negative terminal.
2 Disconnect the ECM electrical connector, EM81.
3 Disconnect the TP sensor electrical connector, PI06 (PI6).
4 Measure the resistance between EM81, pin 10 (N) and PI06 (PI6), pin 03 (N).
Is the resistance greater than 5 ohms?

Yes
REPAIR the high resistance circuit. For additional information, refer to the wiring diagrams.
CLEAR the DTC. TEST the system for normal operation.

No
GO to D2.

D2: CHECK THE TP SENSOR SENSE CIRCUIT FOR SHORT TO HIGH VOLTAGE
1 Reconnect the battery negative terminal.
2 Turn the ignition switch to the ON position.
3 Measure the voltage between PI06 (PI6), pin 03 (N) and GROUND.
Is the voltage greater than 3 volts?
Yes
REPAIR the short circuit. For additional information, refer to the wiring diagrams. CLEAR the DTC.
TEST the system for normal operation.

No
GO to D3.

D3: CHECK THE TP SENSOR SENSE CIRCUIT FOR SHORT TO GROUND
1 Turn the ignition switch to the OFF position.
2 Measure the resistance between PI06 (PI6), pin 03 (N) and GROUND.
Is the resistance less than 10,000 ohms?

Yes
REPAIR the short circuit. For additional information, refer to the wiring diagrams. CLEAR the DTC.
TEST the system for normal operation.

No
INSTALL a new TP sensor.
REFER to Throttle Position (TP) Sensor in this section.
CLEAR the DTC. TEST the system for normal operation

Here is the ECM Module Connectors Pinouts for AJ27 Engine (click on the image after the dropbox.com webpage opens to get a sharper view):

https://www.dropbox.com/s/5j2bftxudq...%20pinouts.JPG

Wire color code N is brown

Here is the Wiring Diagram showing the ECM & TPS Wiring:

https://www.dropbox.com/s/80jqj04ea2...%20Diagram.JPG


Jim Lombardi

 

Thank you all for the answers!

Jim, you are very careful for details as usually, I was using the pdf Workshop Manual 1998 MY on and the electrical guide 2001 on; if you have a link for the newer version of the Workshop Manual it will help me a lot.
I will search for a second hand TB, as shipping to the states for a refurbish is out of discussion.

I know that for some cars, ex my VW Beetle, there is a TPS alignment procedure, is it the same on Jag? I remember somebody pressing the butterfly valve with the fingers (remembers the old cable choke times) right when I started having the trouble.
I also feel that the car don't have the same power as it used to, like not receiving enough fuel, remember the old carburetor times.

 

I just removed the TB, after measuring all the pins like in the manual, no readings indicating a short in the harness, just the last test point had some figures sending me to fit a new sensor (resistance was 750 kOhms versus 10 kOhms recommended).
Cleaned the TB, but it was very clean anyway, fitting back, starting the car, drove OK 10 minutes and,..., it happened again. P0121 was seen on the scanner.
Clearing the codes again, warming the car in P, then drove a little , no codes, no failsafe mode...

Are the later cars known for TB problems? If I buy a used unit and I have the same symptoms, it would be bad!

 

Hi Flay
There seems to be a Chinese manufactures that sells TPS sensors for Jaguar X Type, Honda, Hyundia, and others, maybe if there is enough interest here on the forum about a group purchase, we can get them to produce these sensors for our XJ model series.

Here is website link:

Throttle Position Sensor, Throttle Position Sensor direct from Guangzhou Sensar Automobile Electronic Co., Ltd. in China (Mainland)

Jim Lombardi

 

Thank you Jim, for sure I may be interested in one of those sensors, the one for X type, 2,5 engine looks like our late type sensors. But who can make a proper adjustment?

Starting from cold today,I was driving for 10 miles, max 70 mph, gently,no problem. Suddenly, it did it again,all those messages on the screen... just stopped the engine checked the codes, erase the P0121 , starts without any problem, without opening the car's door. One mile later, again, same messages, plus P0121. Erased and drive away.
As I didn't move any wire on the engine to improve the contact and it started after, I think that the problem is inside the TB, maybe the sensors, actually 2 potentiometers are not speaking the same language after a certain number of beers...
Is it any dealer software that can check the 2 sensors and to pair them? or to reset both? seems simple but not so easy probably.

I just remember, searching in the other TB threads, that my car was/is underpowered, pedal to the metal didn't pull or makes the noise like in the past, (only in S) and that few days back, I heard a very unusual noise when the engine was off with the contact on, like a noisy electric motor, clearly not the usual noise that was in the past(I told that in my old thread).

 

You may want to read this about the TB and my experience with it. Link JagRepair.com - Jaguar Repair Information Resource I also have a rebuild of a TB on my page by Mike’s that might help if you wish to take it on by yourself Link JagRepair.com - Jaguar Repair Information Resource You need to understand that the TB being addressed is for a 1997 xk8

I hope this helps.

 

Flay, we've discussed this particular fault at length in the XK8 forum - it lies in the duel 'tracks' in the potentiometer / TPS sensor. It isn't giving readings to the throttle pedal position sensor or TPPS. Your guess is correct. They're not talking to each other. It just gets worse.

Most AJ27 throttles I heard on startup whine and click. There is an option in factory software to update the throttle calibration to something like 'VBBX'...This along with the latest ECU update is nice to have, but won't fix the worn out tracks, a S/H throttle or a rebuilt one are your options right now. New cost is sick money, like over 1000 euro....

 

Hi Gus
Great info in that PDF file (APP repair) on your website.

My PDF reader opened the PDF file with zoom level of 199% and provided a much improved view of the 3 pairs of brushes.

Maybe one of our forum members will try the procedure on AJ27 Throttle Body.

Someone might at least try to dismantle these Throttle Body sensors and take some photos of the parts that make it operate properly.

This could lead to finding an inexpensive fix on a very common repair issue.

Jim Lombardi

 

A few days ago and today I drive it the usual 10 miles commute, plus some town driving and it was fine; the tester was plugged on, just waiting to clear the codes in case of...maybe the tracks of the sensors(2 potentiometers in fact)are worn in the upper part of their circuit and it is OK when the rpm are lower (up to 2500 rpm) but after, the tracks have some "missing metal" and one is slipping, sending error codes.
Monday, it's the MoT time, fingers crossed... my spare TB will come next week.

 

Just fitted today the new TB, it was a lot dirtier than mine,the same numbers on the body, but it worked.
No more codes on the screen, but I still can say that when I press it hard it seems less power. When I removed the old TB I seen some oil in the "pocket" bellow it, in the manifold, is it normal?



I seen the 130 today in S and a P0300 short time after I putted some injector cleaner in the tank; any possible connection?.

 

only real test is miles. You can test the old throttle pot with a multi meter. Has your OBD reader got a reading for throttle percentage?

Oil in the elbow, have you got an egr valve?

 

I drove it about 100 miles today, the consumption is a little higher than usual. The EGR is there as fitted by the factory (I deleted only on my Land Rover), throttle opening on the OBD reader is about 2-3% on idle and up to 89-93% on full pedal. I tried the throttle adjustment by flipping the square plastic holder on the cable but I want to be moderate. What is the normal opening on idle?

 

idle opening is normal, have you done a hard reset? this is vital when fitting such an important electrical item. Let the throttle recalibrate and let it idle or 10 mins to store new values. This is the most likely fix your consumption issue.

 

Ok, I did a hard reset, letting the engine idle for 10 minutes or more. I seen also a procedure with 45 seconds on 950 rpm, then on 1200 and 1500 for 30 seconds, with the car in D and brake pressed.
Just replaced the gearbox oil yesterday (14 kmiles with the last oil, changed 3 times 3 years ago), P1111 on the reader today... It feels better, but still no pulling like on old times... maybe some vacuum hoses change will improve the drive.
I am happy for solving the TB problem (for now) with only 75 pounds including delivery and my MoT solved(with the old one).
Thank you to all pointing me to the right directions in this and also on other threads with this topic.
Last question: any place to refurb the TB in Europe(I seen bba-reman but how is it)?

 

It happened again, with the second hand TB,after normal driving for 15 miles, suddenly, restricted performance, gearbox fault and other bad news; the codes were P1121 and P1796. Cleared the codes, no more problems.

 

could be the connector or it's wiring to the tpps, if it still does it?

 

I dropped my 1997 XK8 at the body shop a week ago for a new paint job. You can imagine how exited I was to pick her up after passing the shop for a week. When I pulled into the lot yesterday, she was prominently on display, glowing like there was an energy source from within.

I cranked her up and she seemed to rumble a bit. I wrote it off to lack of use fore a week. As I pulled out of the lot I headed to the gas station but the old girl continued to gurgle and finally lose some of her power causing the check engine lite to illuminate and flashing several engine performance problem codes as well a gearbox fault code.

When I returned o the body shop to enquire if they had inadvertently done something, they were expectedly very defensive. "We don't work on engines, we just painted the car" was the reply. I asked if perhaps something could have been blown into the engine compartment when the front bumper was off, but I was assured that nothing like that happened. They did however say that they sprayed the engine compartment out to get the dust from he buffing of the car cleaned out.

So, I brought her to my mechanic who sick discovered that 4 of my spark plugs were submerged in water. He dried he holes out and cleared my codes. It runs fine now, but it was a scary drive to the shop imagining the worse. A brand new looking car that might need a new engine.

Beware of the body shop, or at least warn them not to wash your engine!

 

It's the one on the left, near the throttle cable? Plus I don't have any insurance that the new TB was good working.

 

With a P1121 code it is going to be your TB not the plug!

 

Same code. I cleaned all the connections and 3 times now I've had the car back up and running well, only to hit a sharp bump and have the car immediately go into fail safe mode. This last time I have driven the car around for 3 days with no problem. Then in a hurry to enter the drive of a business, I hit the entrance drive lip sharply and boom…fail safe mode.

I checked and rechecked all connections. And when up and running correctly, I tried to duplicate by tapping connections with screwdriver handle, but could not cause the fault. It is the TPS and throttle body?

BTW, the black box on the firewall that all the wires run into, sure seems loose. Even after I opened it then closed and snugged the bolt down.

"Frustrated"