1G Could it be the TCU?

[Gs Dewd]

I have a problem I hope you can help with. My car is a 94' n't, I swapped the engine for a 91' 6 bolt turbo engine about a year ago and retained the 94' n't f4a22 tranny. Well the tranny finally let go and I got a 92' f4a33 tranny to replace it with. Got the trans installed and car back up and running. The problem is if I use the tcu from the n't tranny the trans will work okay until it goes to shift into o/d. It shift in and out of o/d then stays in 3rd. After it goes through that process I lose 1st so I have just 2nd and 3rd left. If I shut the car off and restart it it works fine again till if goes into o/d (4th). By the way this is a newly rebuilt tranny. Okay so I get ahold of the tcu for the trans and rewire my harness for it (the 94' has different connectors for the tcu) added the connectors to the exsisting harness. Well with that tcu the car is in limp mode no matter what. Stays in 3rd, can't manually shift to lower gears or anything. My question is what could be the problem? THe car seems to work fine with the n't tcu until 4th and goes into 4th just kicks back down the 3rd so I would think by this that the trans is good and the wiring is good. Could it be the tcu? As in the n't tcu being the wrong one and maybe the one that came with the trans being bad? I hate to go through the expense of getting another tcu to find it maybe something else. Any help would be greatly appreciated. Thank-you


John

 

[jabinya]

Strange problem! When my tranny was stuck in limp mode I thought it was my TCU as well. It ended up being a bad Park/Neutral switch.

I would try running test on all the sensors to eliminate that from possible causes. The 1G and 2G technical manual explain how to do the diagnostic tests.

It's strange that your symptoms change when you switch TCUs. Any CEL codes relating to trans problems?

 

[Gs Dewd]

No cels but I did have to chance to get the car scanned today. Here is what was found. With the 94' n/t tcu (wrong one for the trans) it came up with 5 things.
1. Gear shiters out of sync.
2. 2nd gear out of sync.
3. 3rd gear out of sync.
4. 4th gear out of sync.
5. Damper cntrl sol. open
Also the trans was saying it was in 3rd when it was in park.

With the 92 tcu the scanner wouldn't even connect.
Could this mean all I have to do is find the damper control sol. and change it?