chrisorbics

Well the car was shifting normally yesterday. I drove it to my garage and found the tcm. The tcm connection was very clean but the ecm had a little green corrosion so I cleaned it up. There was a very small amount of water in the box. The bolts on the tcm have light corrosion. I would have taken the tcm apart but it is riveted together.

So after that I started up the car and it was starting in high gear and would not shift manually again. So I shut it off and then started it back up and it was back to normal. I am really starting to think that this is an electrical problem.

chrisorbics

Also trans codes came back after driving the car home.

chrisorbics

ok just went outside and started up the car and before moving the car put the shifter in manual mode. It would not shift. Shut the car off and started right back up and it works. Also this time it gave me the message about depressing brake pedal to shift gears which it did not before. Very odd. Has anyone had a similar issue or have any ideas?

hillpc

I get the depress brake pedal message all the time on my 1997 A8Q. Had it before I rebuilt the trans for a blown A drum and after.

chrisorbics

I'm going to see what it does today. I noticed the prnd4321 gear indicator in the gauge cluster looks different and like I said before it will only allow me to select D. If it does this then it will start in 4th gear. I then shut the car off and start it back up and it works fine. The transmission shifts great.

JAA 4.2

If the transmission output shaft sensor, TOS, fails, it will default to 4th gear. It's above the catalyst on the passenger side on the side of the trans around 3 o'clock. Mine came partially unplugged and gave me all sorts of weird issues. It's a 2 pin connector that is the same type as an old fuel injector..

chrisorbics

Ok so the car has been doing the limp mode 4th gear start randomly but very often. Every time it does it I can shut it off and restart and then have no further issues. I have checked all of the suggested plugs and have not found anything off issue.

When I changed the passenger side rear o2 sensor I found some water on the floor that had gotten to the o2 sensor connector. I could have just cleaned the corrosion but I had a new sensor bolted in already. Is there any electrical connectors for the transmission that are in the passenger foot well area?

From here I am ordering the transmission filter kit and if this does not solve the issue I will be looking for a used transmission computer.

twentysevenlitres

I would be changing the F125 selector switch on the transmission before playing about with TCUs.
The F125 is a common fault.

Audipages have a write up about it and the bloke who wrote it even had similar sounding issues to yours (intermittent limp mode).

chrisorbics

I am going to search for this write up today.

I ordered a filter and I was wondering how long the neck is supposed to be so I can see if I need to cut mine.

jfrahm

Round (not oval) and 3/4" (not 1"). Do not forget the O ring on the outlet, get that on there early.

After you drain the ATF, there will be a bunch left in the pan so put the drain plug back in and be careful not to slop it all over when you drop the pan. Then you get another dump when you pop the filter off, and then the trans will rain ATF for an hour so keep that in mind.

If you are putting in the TransGo valve, which I recommend unless your trans is already too far gone, you get more ATF dropping out when the lower VB is unbolted and removed. IMO the only things a fluid change might fix are:
Underfilled (leaked?) fluid related issues like slipping or slow changing into 4th
Shudder from TC lockup due to lack of friction modifiers or too much crap in the fluid or something like that.
Wallet too fat
Driveway too clean

-Joel.