Greetings, I drive a 2004 xtype 3.0 with about 115,000 miles. Last year i was experiencing the gearbox fault message while driving in the rain. I disconnected the TCM and cleaned it along with the connections (from water damage). This fixed the issue up until now. While it was raining the light came on and the gearbox fault message displayed. After cleaning the TCM and connections again, and clearing the codes, they instantly appeared again. The only code I am getting is the P0763 (Shift solenoid C). The car was driving and shifting just fine up until the light came on, so I am considering a possible TCM failure rather than solenoid failure. Also, my battery terminals were in pretty bad shape before I cleaned them, the battery is also showing a high voltage during idling (about 15.8 V).

Would a TCM failure only show this 1 code? Also if I replace the TCM with a used one, do I need to reprogram it? I attached a picture of the TCM to show the damaged area. Please let me know if anyone has dealt with this. Thanks!

 

Now I am getting P1643 code as well. Also, my backup sensors are not working when reverse is engaged.

 

So I ended up replacing the TCM with a used one for about $200 and it worked! Turns out the old one was beyond saving. No reprogramming was needed. I also cleaned out the connectors to the transmission itself (JB155). I uploaded some pics to show where the connector is located on the transmission. There are 2 electrical connectors attached to a bracket that is held in by 3 hex nuts. The first picture is a top down view of the connectors with the battery and tray removed. The 2nd is a view from under the car.

 

But have you fixed the leak? If not, the next downpour is likely to cost you another $200 and probable inconvenience!

 

I'm starting to think it is not a leak that is doing the damage. I had the last TCM sealed tight, and there was no way water could have entered. Still, it got fried. Besides, the rain sensor module sits right on top of the TCM, and it shows no signs of water damage.

I believe the problem comes from the entire car shorting out from the rain. I have been cleaning/maintaining the battery terminals and ground points, and I have not had a problem since. I also put some di electric grease on the problem areas on the TCM and connector, just to be sure.

Here is where I believe the problem starts, corrosion on the negative battery connector/terminal.