Hello, I am having issues with my 1994 Jaguar XJS V12 6.0 L and it activating a Limp Mode after being run for 10-15 minutes. My mechanics have been troubleshooting every possible scenario and though have eliminated many possible causes, we can still not figure out what is causing the transmission to activate the Limp Mode. We are almost at a dead end, and are trying to see if we can contact anyone through Jaguar in UK who could be familiar with the issue.

My mechanic in FL, Paul's Jag, only works on XJS' for the past 30+ years and he has never seen anything like this before. Has anyone at the forum here experienced this before or can give some insight?

Thanks,
Randy

 

Randy,

Perhaps start by checking / changing the Transmission Power relay which is located in the Right Rear wheelarch. It has been known to cause problems when the car reaches operating temperature. It's also one of the infamous "blue relays" for which Jaguar issued a service bulletin in 1997 to change them.

Good luck

Paul

 

If the 6.0 has a TPS, it needs to be cleaned or replaced. Ive been through this with the 4.0L and cleaning it fixed my issues.

 

The V12 has a completely different transmission and fuel injection system than the 4.0. Applying 4 0 fixes are unlikely to work. The 4L80E TCU has a blink code readout if you access the TCU and ​​​ short pin A8 to ground for a couple of seconds a day count blinks on the transmission warning light. Attached is a list of the blink codes. Of course, the easy way is to find someone with a working PDU and read the codes thru the OBD connector.There are 4 solenoids inside the transmisdion, as well as an internal harness that can fail. There are external sensors also. Either blink codes or direct reading with a PDU are really the only ways to troubleshoot the issue.​​​​​​​​​​​​​​​​​​​​​​​​​​​​

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youre right! The transmission is the GM TH variant, Ive never owned a v12 so those details havent sunk in for me.