Ok this is getting annoying.

In short; go through the car wash or drive in the rain, car throws a "gearbox fault" error on the dash. Doesn't shift properly and acts weirder than usual.

Ignition cycle after a few minutes, no error.

I have only been able to find a few posts about this and one mentioned water dripping down the hood release onto the TCM behind the drivers side kick panel. Checked there, bone dry. Another post mentioned removing the TCM and doing some cleanup with DeOxit and sealing the TCM with some caulk. Have not tried this yet.

So before I go tearing into that, is there anything else I should look at?

Side note, even without the car wash, the trans does have a bit of an attitude. At times she will slip out of first randomly and recover...and takes a long time to engage into drive. (I know this is typical and I saw the learning procedure. Also need to try tightening the cable)

-G

EDIT: Did a better job searching using "water" instead of just car wash. My bad. I'll see what I can find.

 

TCM isn't there, it's inside the gearbox, totally sealed.

You mean PCM. Controls the engine. Engine issues can upset the gearbox.

Look to see if water is draining away from the PCM. People often let drains get clogged up.

Check inside the engine bay for anything getting wet in the wash. Electrics & electronics don't like water. From the factory all is god but the cars are now old so things can fail/leak.

 

Just to confirm, is your car a pre-facelift model? You had mentioned the TCM, but this is a separate module found only on post-facelift models.

The early models have the Ford 5R55N 5-speed transmission. At the base of the shift lever, aft left corner, the highest number is 4 (D=5). The transmission and engine are controlled together by a single Powertrain Control Module (PCM).

Later models have the ZF 6HP26 6-speed transmission. At the base of the shift lever, the highest number is 5 (D=6). There's one module for the engine, and sealed inside the transmission is a separate Transmission Control Module (TCM).

Your signature says 2002, so that should be a pre-facelift 5-speed, but I wanted to be sure.

With a Gearbox Fault message, you should be getting a corresponding fault code. A simple OBD reader or scanner can read some (but not all) of these codes. Basically, if the fault could affect emissions (not going into high gear, for example), it will show up on any reader. If not emissions-related, you may need a dealer-level scanner (or comparable) to see the code.

Here's my experience with a Gearbox Fault message on my '02 V6 5-speed:

https://www.jaguarforums.com/forum/s...-p0745-205599/


Since your fault only appears after a car wash, I'd investigate the connector on the left side of the transmission. It may need a little love and De-Oxit. Details in the link above.

 

Correct, 2002. Pre-face lift.

Read through your linked post, lots of good info. I agree, I bet the connector has something to do with it. I’ll tackle that this weekend with some de-oxit. While I’m under, I’ll check out the shifter cable as well.

Updates to follow!

 

So I want to tackle this, but I’m a bit skiddish.

Had my mechanic put it up on the lift and he couldn’t understand what I was getting at. He’s a great mechanic, but we do sometimes have different ideas on certain things.

Can I get to the connector without having to take a bunch of stuff off or out of the way? Is it something I could do if I put the car up on ramps and a little patience? I saw in your notes that you mentioned not pulling the connector out all the way to avoid getting dirt in the transmission; is that still the case here? (I’m assuming I can’t properly clean the connector without removing it completely, but could be wrong)

I also have a small amount of play with the shifter, put the two bolts mentioned in other threads are tight. I’m guessing it’s the “stretched” cable, but I’m wondering if there is a way to adjust it just a touch to resolve. This isn’t an issue, just a little annoying is all.

 

Disregard comment on removing the plug, I re-read it and understand what you were getting at by not letting the plug body become detached and let dirt into the trans. With the tight access and captive bolt, I’m still a little hesitant.

Still curious as to thoughts on the small amount of shifter play. Checked the bolts, they are both tight. Mechanic mentioned its likely the shifter module (the same module which I believe causes the shifter to stick in park when the plastic breaks). As luck would have it, I already ordered a replacement. I plan to replace myself to avoid having that plastic break at the wrong time; the replacement I ordered is the “upgraded” version with metals parts. If that takes care of it, awesome. If not, at least I’m avoiding that horrible stuck in park issue.

I’ve also read some things about the metal contacts mounted inside the shifter assembly which tell the car what gear it’s in. Perhaps something to look at as well?

 

The "problem" with the shifter is essentially due to not applying the parking brake before putting the car in Park. Most cars you can get away with that, but you're still putting (part of) the weight of the car on something not really designed for that.

 

The shift lever module itself is not the root cause. The plastic piece inside is the weak point that breaks when too much force is applied, but the basic design of the park pawl in the transmission is what creates the whole problem. The 5R55N is a Ford transmission, and this issue is a known problem with this entire transmission family. The following thread is a good example. It's a bit of a mash-up discussing both the 5R55N and later ZF transmissions, so jump to post #6:

https://www.jaguarforums.com/forum/s...ncline-183486/


With any automatic transmission, not just with my Jaguar, I've always followed what my Dad taught me:

1) Stop car with foot brake.

2) Shift to N while holding foot brake. This relieves any load on the transmission.

3) Set parking brake while still holding foot brake.

4) Release foot brake and let all weight of car settle on the parking brake.

5) Press foot brake again and shift to P and you're done.

With these quick steps, the parking pawl in the transmission is engaged, but has no weight against it. The parking brake is the primary thing holding the car. The pawl is the backup, a very robust one, I must say.

Sounds like a lot of work, but not really. It's a quick process I can do on autopilot. If you get in this habit, your transmission will thank you.