I cannot find anyone who can diagnose the transmission fault code in my 1990 xj 40. I need to know what diagnostic equipment is used to perform this task. jag dealer says they can't or won't test it. I have taken it to two independents who said they could but didn't. I have went through the diy test procedures. somewhere in here I saw a post that named the equipment... can't find it now. plz help.. What type of equipment is needed to test the transmission fault code in my car? I feel like I am chasing a ghost. tranny in limp mode..

 

Are talking about your VCM? Just turn the key to run but do not start it, press the VCM button and it will show your fault codes in priority order. You can see all by displaying them and clearing them one at a time by grounding the red connector under the right side knee bolster to a body ground for three seconds, that will clear the codes in descending priority should you have more than one code flagged. PM me if you need more details, bu first see if you have a CEL and any codes from your VCM

Charlie

 

The only diagnostic computer that I know will work is called PDU (portable diagnostic unit). Most of them have been discarded by the Jaguar dealers, have a dead battery pack or they have a broken CD ROM.

Most common faults are bad relay for power supply or TPS fault. Could be a wiring fault or harness connector.

Call Jaguar dealers in the area and ask if they still have a working PDU.

bob gauff

 

Thanks Motorcarman! VCM produces nothing sleepycat. no fault codes at vcm and no check engine light but still in limp mode. I have replaced the tcu, the decoder module, the relay and did a minor harness repair to no avail.I cleaned and checked the rotory switch and I tested the throttle potentiometer. It is not in spec... I get 5mv down to 1mv. I will try replacing it and see if that works... tnx

 

I think it is a very good possibility that the TPS may be the source of your problems, no codes but limp mode and the TPS out of spec seems to be your demon. Too bad you didn't check there first, could have saved some $$ on those other parts. Good luck, let us know your outcome!

Charlie

 

The PDU will read ECM, TCM and ABS codes. It will also help calibrate the TPS but that can be done with a Volt Meter.

The TPS setup is described in the S91 publication I uploaded a few years ago.

bob gauff

 

Motorcarman., I may have rushed my reply... I removed the potentiometer.. trying to save the one I have. Anyway .. doesnt look like it comes apart like the rotory switch does. cleaned the outside and soaked it down with contact cleaner. Out of the car I can get it to sweep from over 5.5 mv(5500 ) to below 250 mv (.25) .
In the car, I cannot get it to go below 1.25mv (1250 mv )at full throttle, .. I could tighten down the throttle stop.? Is there a procedure to calibrate it with the tcu & ecu ? Should I get a new one? the specs as far as I know are 5.5 or 5500 mv at rest and 250mv or .25 on my meter at full throttle.
I am stuck again, any help is appreciated.

 

I cant find your s91 info..

 

Found the download... What is your advise? Seems like I may have to find someone with a working pdu?

 

reedster, did you solve the issue?

 

Marco,

Please note that Reedster's last post in this thread was more than 4 years ago.

I wish someone would have told Reedster about the transmission diagnostic procedure in the Jag-Lovers online eBook. Have you had a chance to follow that procedure yet?

Cheers,

Don