1G Transmission "Limp Mode"

[krimsonrider]

Summary: 92 eagle talon n/t automatic transmission. When put in drive, stays only in 3rd gear. Shift pattern selector and overdrive switches signal they work but no change! All cables are adjusted properly.

Is my TCU dead? How can i diagnose this myself? This is the first automatic ive owned any information to point me in the direction i may need will greatly be appreciated. Thanks

Alright so I havent found out why my tranny is in limp mode, yet. But dont despair! Im a very persistant person and I came across a page researching the subject. This link will be very helpful to those DSMers with Auto trannys trying to figure out problems.
http://www.plymouthlaser.com/tcucodes.htm

 

[talon91tsiawd1]

hey i dont know how to fix your problem but if you need a tcu i have one out of a 91 tsi awd auto!

 

[dieseltech]

Remove the TCU and inspect the caps. Or if you have acess to an analog Dvom you can take a reading at the data link connector. If the reading is a constant voltage, including 0 volts, your tcu is dead. I had a dead tcu. I diagnosed it by checking the data link connector. When I inspected the caps, I found they had exploded. And that 91 awd tsi tcu won't work.

 

[steve]

The TCUs shared the same bad 47uF capacitors found in the 1G ECUs. The only difference is that those in the ECU don't usually cause the 5v power rail to go to 12v when they go bad like the design of the TCU does. Feeding 12v to chips with a max voltage rating of maybe 6v isn't good for their health and about half of the TCUs I tried to fix were permanently fried because of it.

A healthy TCU like the ECU will put out a alternating on off heartbeat on its diagnostic pin. No voltage or always 12v indicates a dead TCU causing limp mode. If the TCU is working but you have other problems you will get codes listed in the link above.

Steve

 

[krimsonrider]

Well I opened up my TCU which is what of should've done earlier and found interesting things...

Well I know now the printed circuit on it is fried, residue from the factory capacitor leaking can be found all around it and on other components. Some printed circuits are even blackened from the corrosion.

So I need a new TCU! Are there any other TCU's with different part numbers for the F4A22 auto tranny compatible? Or do I have to go with the original P/N? Thanx.

 

[dieseltech]

go wth the original part number. you may be able to have someone with caps tell you if there are any supersessions and such. I've read that a 1.8l tcu will work, but i cannot confirm that.