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I have replaced a blown capacitor and the throttle motor driving transistor on my MY1997 XK8 ECM board, but the XK8 is still coming up intermittently with
"STABILITY & CONTROL FAIL" w/Amber Warning Light on dash & code P1791
"GEARBOX FAULT" with Red Warning Light on dash, which means I'm in limp-home mode stuck in 4th gear only
"ENGINE FAULT" with Red Warning Light on dash & code P1224
The above faults can appear independently, or in pairs, or all three together, at random times. I can make these warning(s)/fault(s) go away by simply shutting off and restarting the engine, until the next fault appears at random at interval of maybe 5, 10, or 15 minutes later or they don't come at all for the remainder of my trip.
According to this extract from Jaguar's Powertrain DTC Summaries
Code P1797 indicates the ECM and TCM fails to communicate with each other.
Column 8 with heading CM PIN refers to GB2 -2 -6. What is GB2? Is it a Module or a Connector pin? Can anyone give me a clue?
There are no more Lucas parts to haunt the XK8. Instead its Nippon Denso and Bosch who supply the ECM and TCM, respectively.
Originally Posted by xkeots
Ok peeps,
Has anyone had the gremlins of Fail Safe with nothing wrong? I need to gain trust in my car again but I don't like getting stuck.
Originally I received the message and code told me speed control. I then took all of the wires off of the throttle and first contact cleaned them with electronic parts cleaner then when dry used dielectric grease.
That seemed to work just fine till I had to pick my son up from a friend late and car went into Fail safe mode. I was able to shut key, restart and it went away. A week later I was going out and right into Failsafe mode after a rain storm. It wouldn't limp it's way up my driveway with a small incline. 5 hours later it started and ran, (no codes on any of those fail safes) like nothing was wrong.
Someone who owned car before me had Jaguar change the one gremlin plug to throttle with mix matched copper/Tin connectors, to all copper. Continuity is perfect zero on multi meter and solder joints perfect.
I just want a car I can get into and drive without in the back of my head it will go limp. I need XK 8 Viagra!😜.
Any ideas on fixing this?
I feel like the Devil spirit of Lucas has followed me from my XK120, MK2 & E-Types here. But there is no Lucas G-d of darkness in this car!
Thanks
Jax
99 xk8 convertible
As I am certain you have already changed out the battery, what is its age and condition?
I find it odd that I have never experienced the 'legendary' Lucas electrical faults that so many on this forum mention. I have experienced faults with other systems such as Bosch, Magneti Marelli and Paris-Rhône, but are usually confined to poor wire or earth connections.
According to this extract from Jaguar's Powertrain DTC Summaries
Code P1797 indicates the ECM and TCM fails to communicate with each other.
Column 8 with heading CM PIN refers to GB2 -2 -6. What is GB2? Is it a Module or a Connector pin? Can anyone give me a clue?
There are no more Lucas parts to haunt the XK8. Instead its Nippon Denso and Bosch who supply the ECM and TCM, respectively.
I'm confused here. You look to be referring to 2003MY or so XK8 codes data. In turn it refers to things in a 2003MY or so car. I thought that was not your car. Please confirm the car you have.
GB2 is in a 2003 car. It's the connector on the TCM. -2 -6 are the CAN pins.
If you have a much earlier car as your sig seems to say then be wary. I'd compare your car's electrical guide to the 2003 one - especially module pinouts etc - to see if they are alike (which I doubt somewhat).
I don't see P1797 at all for the car you appear to have. That may mean you're getting some sort of phoney code or it may be that jag updated the (PCM/TCM/...) software but we don't have matching codes data. I do not know the actual situation.
If you keep getting CAN errors such as P1797 then how often? It's a lot easier chasing a fault that occurs all the time. Otherwise you end up wiggling cables etc and with access to some of the connectors being "awkward" that is a major pain.
Er, that ASSUMES that P1797 is a CAN code. The thing is, P1 codes can change at will since they are non-generic and that means they can change by make, model, year, anything. We do have a P1 code for the S-Type that changed dramatically between model years.
Thank you very much for your reply. A brand new battery was installed by the previously owner on the day he handed her over to me 35 months ago. Is is a Bosch (made in Korea) no-refill type rated at 100AH with a single window showing green/red/grey for normal/recharge/replace status. Just took the voltage at 12.26 volts after sitting overnight at 50°F/10°C. Do you think I should take it to a shop to have the starting current tested also?
Some member suggested with these intermittent faults, a poor ground or multiple poor grounds may be the cause, but I am totally lost at where to start to look for that. The problem is still unresolved...
Originally Posted by NBCat
As I am certain you have already changed out the battery, what is its age and condition?
I find it odd that I have never experienced the 'legendary' Lucas electrical faults that so many on this forum mention. I have experienced faults with other systems such as Bosch, Magneti Marelli and Paris-Rhône, but are usually confined to poor wire or earth connections.
The battery voltage is too low, should be at least 12.5. The major electrical connections are at the big fuses just forward of the battery, the bulkheads at the fuse boxes, the starter and generator, and the engine to chassis ground on the right side of the bell housing. The latter especially should be taken apart and cleaned.
The negative battery cable should be removed from the battery before proceeding and both battery terminals also should be cleaned.
Thank you very much for your reply, and your very sharp eye detecting my extraction from the MY2003 DTC Summaries.
Originally Posted by JagV8
I'm confused here. You look to be referring to 2003MY or so XK8 codes data. In turn it refers to things in a 2003MY or so car. I thought that was not your car. Please confirm the car you have.
My XK8 is indeed MY1997 as stated in my signature. The DTC listing closest to my MY which I can locate and has an entry for P1797 is MY2003. Sorry for confusing you, but the fact remains I continuously pull P1797 like every 5 minutes driving, and I need to get to the bottom of it ...
GB2 is in a 2003 car. It's the connector on the TCM. -2 -6 are the CAN pins.
If you have a much earlier car as your sig seems to say then be wary. I'd compare your car's electrical guide to the 2003 one - especially module pinouts etc - to see if they are alike (which I doubt somewhat).
For MY1997, the TCM connector is an 88-pin EM7 which connects to a BOSCH TCM. Does it bear any resemblance to the GB2?
I don't see P1797 at all for the car you appear to have. That may mean you're getting some sort of phoney code or it may be that jag updated the (PCM/TCM/...) software but we don't have matching codes data. I do not know the actual situation.
If you keep getting CAN errors such as P1797 then how often? It's a lot easier chasing a fault that occurs all the time. Otherwise you end up wiggling cables etc and with access to some of the connectors being "awkward" that is a major pain.
The ECM on my XK8 has a label dated 2011 from AutoECU aka ASI who fixed it before I bought her. How can I determine from what MY was my ECM extracted from?
Er, that ASSUMES that P1797 is a CAN code. The thing is, P1 codes can change at will since they are non-generic and that means they can change by make, model, year, anything. We do have a P1 code for the S-Type that changed dramatically between model years.
Thats all the leads I have to solving my intermittent fault(s) for now. Stay tuned...
Thank you very much for your reply. I obtained the 12.26 volt reading with the OBD II scanner connected overnight. I've now pulled the OBD II scanner and shall get another battery voltage reading tomorrow. Bear with me.
Both battery terminals are VERY clean. I'll check the major connections you've provided, too. Thanks.
Originally Posted by RJ237
The battery voltage is too low, should be at least 12.5. The major electrical connections are at the big fuses just forward of the battery, the bulkheads at the fuse boxes, the starter and generator, and the engine to chassis ground on the right side of the bell housing. The latter especially should be taken apart and cleaned.
The negative battery cable should be removed from the battery before proceeding and both battery terminals also should be cleaned.
The ECU is probably the original repaired by ASI. Check the back of the spare tire space for the VCATS list. It will list the ECU among others and you can compare with the label on the ECU. It should be LJA1410 AJ or similar.
12.26V is probably OK unless it's with a reliable meter with engine running when it would mean your alt. is dead.
You can compare electrical guides across MY cars with some effort. I just grab both PDFs and open them outside JTIS.
At a guess jag updated the software but not JTIS. It happens.
To keep getting a CAN fault (let's hope the guess re software is right!!) you pretty much have to have a bad connector/wiring relating in some way to CAN. Or maybe power to a device on CAN. I'd check first for chafed wire or bad/dirty connector. Wiggle test.
Modules seem far more reliable than the above but still it could be a module I suppose.
ASI repair label stuck on cover of ECM 1st rebuilt in May, 2011.
Blown capacitor in ECM. Feb 2016.
Charred PCB.
560 uF 50V catalytic capacitor
Originally Posted by RJ237
The ECU is probably the original repaired by ASI. Check the back of the spare tire space for the VCATS list. It will list the ECU among others and you can compare with the label on the ECU. It should be LJA1410 AJ or similar.
I cannot explain what has happened, but after driving her for the past 5 full days, she has not thrown a single code nor warning light. It appears she has cured all of her illnesses/faults without any of my intervention(s).
The front shock mounts both left and right side have been disintegrating due to age the last two weeks, generating excessive shocks/vibrations. Maybe this action restored all the poor groundings/connections which caused all the intermittent faults.
She has behaved beautifully these past 5 days, and I'm loving this miracle.
I was keeping my fingers crossed after your post, hoping the Big Cat will stay healthy indefinitely... but it appears the "virus" within the ECM/TCM has mutated to a slightly different form after a 7~10 day trouble-free running period. See my new post https://www.jaguarforums.com/forum/x...ng-lit-159933/
Any ideas how to get it fixed?
Originally Posted by RJ237
Now you're in for it! Putting that in writing is just asking for trouble.
The blown capacitor and the throttle motor driving transistor in the ECM have been replaced in the previous episode and car went back to normal for about 10 days and now a slightly different problem has appeared. See new post: https://www.jaguarforums.com/forum/x...ng-lit-159933/
Will take the ECM out again to have a second look...
Originally Posted by brgjag
These do not fix themselves. If that ECM has that burned up part, it needs fixed.
Intermittent Gearbox/Engine/Stability Control faults
