1991 Gran Prix, 3.1 (vin T) and 4T60, need wiring schematic!

[ssjerry]

176,000 miles on daughters car. I am in the process of replacing the 2 engine wiring harnesses. I got the harnesses off a 4 door 92 Regal Custom (according to vin number) also with the engine code T. (GP is a 2 door). It took me several hours to find a car with the same harnesses that hadn't been cut up by someone removing a sensor etc. I guess there was one plug that I didn't verify was identical and that is the plug that connects to the auto trans. I still think the Regal had the same trans but mb not. According to my Chiltons, the 92 Regals only were built with 4T60 and I knew thats what I had.

Anyway, my GP trans has a 5 wire circular plug and the Regal harness has a 4 wire square plug. Whats strange is that the Chiltons schematic groups all 91 to 93 W-bodies with T code together on the same wiring diagram with 5 wires to trans. Haynes manual shows 7 wires for trans for 93 and earlier. It appears that the Regal wiring is missing the light blue wire running from position B on trans plug to position D22 on ECM/PCM.

I was hoping to verify this with the actual wiring diagrams for each car model. If that isn't possible, can someone familiar with these cars and transmissions confirm my thinking on just running a new wire for the one I think I am missing and changing the trans plug back to the 5 wire round plug. Are the other four wires still connected to the cars the same or do the two models have totally different connections for their transmission.

I thought that I had read in other posts that this trans wasn't an electronic transmission anyway. If so why does it need 4 or 5 wires? It seems like all it needs is one wire for the TCC.

Thanx for any responses to my first post. This appears to be one of the most informative and responsive forums that I have seen.

[Robby1870]

The trans isnt electronic. The 5 things that are controlled are 1) 1st gear pressure switch, 2) Shift solenoid A 3) 4th gear pressure switch, 4) Shift solenoid B, and 5) Torque Converter Clutch (aka lockup).

 

Here are the colors for the wires I am showing for the above number

These are for a 3.1L equipped car

1) Red

2) Orange

3) Light Blue

4) Lt Blue

5) Tan/Black

 

Now, you said that the Regal you got the wiring harness from had a 3.1L. However, you said it had a 4 prong connector to the trans. Now, the regals that had the 3.8L had a 4 prong connector to the trans, with the following wires

1) Torque Converter Clutch PWM Solenoid, color Dark Blue

2) Shift Solenoid A, color Light Green

3) Shift Solenoid B, color Yellow/Black

4) Torque Converter Clutch Enable Solenoid, color Tan/Black

 

Now, Im not trying to be an mean or a dick or anything, but are you sure the Regal had a 3.1L, and are you sure it had a 4T60? Again, Im not trying to be an ass, Im trying to figure this thing out. Cuz, its not adding up.

 

I dont know if you can run a wire from the GP ECM to the tranny. I dont see off hand, why you couldnt, but Im not for sure. I hope some or any of this helps

 

Robby

[ssjerry]

the Regal I got the wiring harnesses from had a vin #

 

2G4WB54T2N1468227

 

which I show to be a 92 Regal Custom with 3.1 built in Canada. I also had to remove the 3.1 plenum to get to the wires connecting to injectors etc. I am not positive on the transmission however. I had enough trouble even reading the ID plate on my GP with everything removed from engine compartment except engine. But I do know that the Regal transmission did have the same plumbing for vacuum running to the modulator, same TV cable and the same wiring connects for the nuetral, gear selector, and speed sensor, and same location for the beforementioned plug.

One thing strange about this GP. Titled as a 1991. Built in October 1990 (nothing unusual). However, when the car was purchased new, it came with a 1990 owners manual.

Some of the stuff in the manual doesn't match the car. I've also noticed that some things on the car don't exactly match repair procedures for a 91 model. I was looking at the wiring diagram for a 1990 GP with 3.1 and wiring colors for the transmission are an exact match.

I do appreciate your help so far but I have to get back to my taxes. Maybe tomorrow I run back to salvage yard and recheck the Regal transmission and look at a few others for reference

[Robby1870]

yeah that regal had 3.1L then. That is pretty strange. Maybe the regal transmission was the 3T40 (THM125-C). I dont know that is really strange though. Or your GP is the 4T60E but with the 3.1L I doubt that. Or, the regal got the 4T60E. I dont know, they should match up though. Go back to that scrap yard look at that Regal, and if the motor and trans are still in it, look at the trans pan and see what it says. And, about your GP, that is very strange, that it has 1990 manuals and what not. I dont really know what to tell ya. Good luck with your taxes

 

Robby