I recently drove my XJR on a cold day, parked it in the garage, and found the familiar trans oil leak from the electrical connector.

I changed out the connector with the kit on ebay for about $40 (Oil, connector, replacement oil tube cap, etc), and filled the trans back to the proper cold/warm levels per the dipstick ordered from ebay.

Upon dissasembly, I did NOT disconnect the battery originally, but before putting it together (while waiting on parts to arrive a week late), I did disconnect the battery, hoping any faults generated pulling it apart previously would be deleted. (only to learn that doesnt delete TCM faults, only ECM).

Now I have the High Trans Temp fault. the car runs and drives but is holding gears to 2000rpm+ before shifting. it is also downshifting a bit hard. I assume this is how it acts in fault mode.

Has anyone had this happen? and does taking the car to the dealer to have the code reset fix this issue? Or do I need to replace the connector / harness?

 

I would say you need to troubleshoot the temperature sense circuit. Have you downloaded the JTIS manual and diagrams? Do you have a DMM? I doubt that any reset is needed after a power cycle.

 

Maybe its one of the pins in the connector. Try reseating the connector.
The driving behaviour itself is suggestive of low fluid.

I have had this message come up and it is transient. No reset required.

It seems to happen a couple of times a year in really wet weather at
the end of a drive.

 

Ok. Cleaned the pins in the trans. Cleaned connector (both male and female parts), re-assembled. Same fault (High temp transmission) but only when in gear.

Double checked fluid level (since I have driven a bit) topped off barely a splash of fluid. Same fault. Checked harness pin for pin, harness is good. Same Fault. The very second I put it in gear.

the only thing I can think is could be the sensor itself, or the shift/start switch? Ever heard of those failing?

 

The temperature sensor is not active in Park or Neutral.

As a first move you can take readings using IDS/SDD to check for
plausibility. For example, start the vehicle from dead cold and
check temperature while in Drive immediately. It should not have
gotten over 100*F in that time.

 

Fluid = good. Harness checks out. I know pin 4 & 12 are closed in park using continuity tester, and I cannot start the car in R or D, so I think its safe to assume the park sensor works. I THINK i've deduced a faulty temp sender?

As I originally stated, when I took it apart before, I had not disconnected the battery. and clearly some fluid had leaked into the connector. I'm wondering if maybe the contacts somehow were shorted and damaged the temp sensor? or if it magically just stopped working when the connector was replaced.

Also - I assume I have to replace the connector plate in the trans to fix the sensor problem?

Im comfortable replacing the plate in the garage, if I could somehow determine oil or something else was the actual factor. I also dont know why it woulda failed while fixing the connector.

Can standard OBDII testers determine if the sensor is working properly?

 

What kind of "oil" ( I guess you mean transmission fluid?) came with the kit?

Shell ATF134 is the recommended type and you can also buy the correct stuff from Jag or Mercedes.

These trannys have very specific requirements for fluid and don't like it when you use the wrong juice. If you mixed some of the original fluid that was left in the torque converter with whatever they sent you from Ebay, you could have a problem.
Vector

 

I ordered a Merc connector plate, in the hopes its a faulty temp sensor for some reason, and I'll at least get a tranny fluid change for pc of mind. Meyle Brand MB Spec 236.10 Transmission Fluid and filter.

 

I dont know what I did that made the sensor fail, but replacing the connector plate did the trick.