A/T downshifting on its own at the wrong time?

[EagleTalonTim]

Here recently, my 93 TSI AWD auto tranny has been acting up. If driving normal, the transmission will downshift to the passing gear and stay there for a few seconds....Kind of like it is trying to go into Limp Mode. I just recently put another computer in the car from a M/T AWD Turbo and also a Glowshift Oil gauge and Boost Gauge. The car did not start acting up as soon as I installed those parts and actually drove and shifted very well. My girl was driving the car and on her way home, the engine started overheating and the transmission got stuck in 2nd gear. I found that the coolant fan went out, so I replaced it with another one and tested it. Everything tested out fine. I reset the computers and took it for a test drive. It still was doing the same thing. Today, I did a tranny service, replaced the filter and the fluid, and cleaned the magnets at the bottom of the pan. There was small metal dust on the magnets. Nothing unusual. Took it for another test drive, and it still tried to jump back into the passing gear. I opened the TCU on my car to see if anything was bad in it. It looks perfectly fine. No leaking caps. The TCU codes that I got were 42 and 44 : Shift Control Solenoids. The transmission was rebuilt 2 years ago, then the timing jumped and it sat for 2 years. The rebuilt transmission has about 1500 miles on it.

I found in a thread on here that it could be the speed sensors. Where are they on the transmission. I have been looking for a picture of them installed on a transmission, but I cannot find anything. Orielly's has them for $16 a piece, but I don't know where to install them on my transmission. Does my transmission even have speed sensors?

I also noticed that if I turn my cruise control on, the tachometer and the temp gauge both stop working for a second. If I brush my foot up against the fuse box area, it will start working again. I have not pulled it out yet to check the connections or for loose or broken wires. I would not even know where to start. Sometimes the cruise works, sometimes it doesn't. If the trans jumps into the passing gear, I can do the same thing by brushing my foot against the fuse box area and it jumps back into gear.....sometimes. I tried letting it go back into the passing gear and not touch anything or change the position of my foot on the gas pedal and it will eventually go back into gear on it's own.

EDIT * Cruise/dash thing has been fixed.....loose fuse. Transmission still acting up.

Please help! I really hate automatics, but my girl needs something to drive till we find her a decent car to buy. I will be doing an A/T to M/T swap eventually. I miss my 5 speed!

 

[EagleTalonTim]

New Update.... I took the car to a transmission shop and got them to put the scan tool on it. Unfortunately, I paid $26 to find out the same thing I already knew. The computer read that there was a short on the shift control solenoids. After getting pissed off that I paid for something I already knew, I checked the solenoids for ohm resistance. I got 3.3 ohms for the one with the orange wire, and 3.1 ohms on the one with the yellow wire. I checked the ohms of the sensor connector from the TCU and got 51K ohms on both of them. I turn the ignition on and put the e-brake on them put the transmission in L. I checked the output voltage of the TCU and it was 5.2 to 5.4 volts. Is this right? Shouldn't the solenoids be getting 12 volts? Can I wire relays to the output of the TCU that will control the power given to the solenoids?

I know this thread is 3 days old, but I really need to get this working fast! I am almost tempted to build my own shift box and run it on my stock tranny. Would the solenoids work sometimes and sometimes not if there was a short in them? Most of the time, the transmission shifts fine and drives fine. It is just every once in awhile that it will kick down into another gear or start out in the wrong gear.

The trans fluid level is exactly in the middle between the HOT mark when running at normal temp and in neutral.

 

[EagleTalonTim]

And yet another update. Sorry for the posts, but I would like to help out those who have this same problem as I go.

I hooked up a meter to the shift control solenoid A (yellow/blue wire) and took it for a test drive to check the voltage going to it. It was 12vdc in first and 2nd gear. I stopped and switched it over to solenoid B (orange wire) then drove it around some more. It had 12vdc in first and 4th gear. Sometimes it did not kick on from a start until I gave it a little gas. Also, as I was driving, the solenoid B would turn off, it would kick into 3rd, then a few seconds later, it would kick back on and drive normal. I am about to say $&#@ it and build me a manual shift box. I don't know what else to check that would cause the TCU to go into limp mode so random.

 

[EagleTalonTim]

Ok....problems solved. I built my own shift box and it works great If you want one, pm me and I will build one for you and ship it at a reasonable cost.