My XJR has a Gearbox fault message and car goes into LIMP mode (It has happened to previous owner but went away by shutting off car and sitting a bit). All summer had no such problems and I always keep it in SPORT mode. During early snow storm traction was bad (summer tires) and there was lots of Traction control/ABS action in order to get the car moving at all. Trying to pull out on to busy road and got GEARBOX FAULT (went to LIMP mode). Made it to Hotel & sat for about 17 hours. Next day snow melted away car started (no Message) and drove fine for about 3 miles until stop sign... when pulling out... GEARBOX FAULT (went back to LIMP mode) parked car at work, disconnected neg then pos terminals and clamped together overnight. next day (17 hrs later) reconnected pos then neg (no Messages)then drove 45 miles home with TRACTION button OFF, Sport mode ON... no problems. When I got near my house I gunned it... supercharger kicked in ok but when I let off throttle... GEARBOX FAULT (went to LIMP mode). I borrowed a OBD2 code reader and only got code p0702 which is
only search info towards troubleshooting I found was:

"That code is either a faulty TCM or you have an open or short circuit in the TCM pins 52 and 53. Pin 52 is the red/yellow wire to the trans shift solenoid and pin 53 red/blue goes to the pressure regulators. The harness sometimes shorts on the driveshaft if work was done to the vehicle and the harnes was disturbed".

I have checked the Transmission control module on passenger side in engine bay and the connectors were pulled they each have numbers but each connector counts up to only 38. I have visually checked the wiring harnesses and look ok. I have a digital multimeter. Anyone have any troublshooting advice or wiring diagrams for the transmission circuits?
Oh yeah, Battery Voltage car off 12.1V, running 14.2V.
Sorry for the long read but I wanted to include all my symptoms

 

You are probably reading a description as it applies to the non-supercharged XJ, which uses a different TCM and different transmission.

The TCM for a SC has a 14 pin and 18 pin connector.

The electrical diagrams can be found in links in the faq.

 

Also check the connector that goes into the gearbox, make sure it is dry/clean and pins look alright.

 

With the MB box you always check the fluid level and then the electrical connector at the transmission at the first sign of any problems. The fact that it does not have a dip stick makes this a little difficult but it does not lessen the importance of getting it done. The connector leak is a very common problem -- and enough fluid can leak out undetected to cause all manner of problems. If it is found to be a problem it can be purchased for around $35.00 -- get a genuine MB connector -- the aftermarket ones have proven to be unreliable.

Transmissions don't magically fix themselves and ignoring unusual operation will only lead to more problems. And the last thing you want to do is rev the engine in gear.

Your car may have other issues since the wires are disturbed -- maybe the connector leaked before ........... any fluid around?


How many miles?

 

Well today I looked at the connector... dry as a bone, I have to get a dipstick to get an exact measurement, So far I have only checked (for color and rough estimate) it with a bike brake cable. It has 80,ooo miles.

 

megawatt whats your color of the fluid looklike? reddish or blackish?

 

You need to read the TCM codes as well as the ECM.
Here are some TSBs for the W5A580 as Jaguar calls it.

bob gauff

 

Thanks motorcarman for the TSBs. I have not seen the linear switch one yet. I am in the process of trying to find a local repair shop that is able to read all of the codes (TCM ect..) Any other way do get the TCM codes?.

The color of the tranny fluid is light brown, not much red tint.

 

Maybe a transmission shop??
I have WDS and it is a common Ford computer from a long time ago. Maybe a shop in your area has one with the Jag software.

bob gauff

 

Fixed!

(for now, lets put some more miles on it) .
I checked the voltages on it several times, while car running as well, looked good and assumed it wasn't the culprit! But low and behold after pulling it out of the car and checking the water levels... I found a empty dry corroded cell on the battery!
Swapped it with a new Duralast from Autozone and put some around town driving on the car as well as some supercharger stomps.. no faults yet, I will post again when certain this was the only problem.

 

Jaguar 98 XJR models suffer from Voltage spikes. Turn on the heated seats and a light comes on. Press the Sport mode and a light comes on. The CAN system is very frustrating to deal with and if you take it to a Jaguar dealer they will simply throw parts at the car until you give up. Go to Amazon.com and by yourself a OBD2 Code reader, the access point is located above your right legs shin under the dash. Trust me this will be the best $100.00 you ever spend.