This Spring, I was driving on the highway going ~65mph, through pretty heavy rain, and my car slammed in to limp mode. I was able to get it home as the highway I was driving led straight there, but the next day the CEL was gone. now about 3 times since then, it has happened. Only when there is heavy rain or if I am driving above 45mph in rain.

It usually takes 10-15 minutes of driving to kick the engine in to limp mode.

Also, last year I was driving around this time of year and the dash needles all went dead and to their resting, off position. No issues with power steering, radio, anything other then that. I parked, went into work, and upon leaving the car hasn't had an issue since.

This leads me to believe I may have an exposed wire, or something is not fastened correctly. Any thoughts to help me start diagnosing the issue?

**EDIT - I get a GEARBOX FAULT message when it happens. But in dry conditions, transmission is very smooth with no hitches.
Thanks!

 

Check around under the dash on the passenger side for leaks from the cowling or windshield. The ECU is mounted under there and points upward at an angle towards the engine compartment. water gets in and set on the ECU and you get limp mode. Once it dries out everything is good to go.
Need to find the leak and fix.

 

Thank you avern! This was the last on my list of things to address and it sounds nice and simple.

As far as sealing it, what type of leak are we talking? Something to be wrapped in electrical tape, or a silicon sealant? I am assuming the latter.

Also, what's your best way to check for the leak? I don't know of a good way, without risking pouring a bunch of water on the ECU myself -.-

 

Check the ECU and if it wet have a partner with a bright light outside and try to look for light coming in. But you might also try a close exam underneath and see if you can see a water trail. Could be windshield seal. Silicone missing around cowling. It will probably be apparent since you hit limp mode pretty quick in the rain.
Also do a search about wet ecu, cowling leaks, and windscreen leaks on the forum. Maybe try limp home in wet conditions. A lot of folks have had to deal with it and you will get some good info from their posts on what they found and how they sealed it up.

 

swetnK,
Check this thread starting with post #7
https://www.jaguarforums.com/forum/x...emedies-72301/

 

swetnK: To disconnect the electrical connector from the ECM, Thermo describes the 5 point security Torx bits you'll need in this post and the subsequent one:

https://www.jaguarforums.com/forum/x...6/#post1304839