Electrical and PCM
 

Hi all, hope everyone is well.
i have a 1991 Olds Toronado base model. 3.8 L V6. 235,000 miles.
I started having various problems last summer with this car. It was running and driving perfect before this all started.
First it would start to die when I was on the highway, it would just cut out for a second and then back to normal, when this happened, the tach would drop down really fast and then back up.
no codes. And VERY intermittent.
it's my second car so it sat most of the winter, I would drive it around the block about once a month with no problems.
Then around Jan, the door locks would get stuck on like somebody was holding down the lock button while it was just sitting in the driveway. Had to unhook the battery. Even if I started the car, they would stay energized.
then I saw a post about the IPC causing Data Line problems. So I took the IPC out and all I found was 1 bad capacitor. everything else looked good. changed cap,
Put IPC back in car, now car started and sounded normal, door locks quit staying on, but now I had no incandescant bulb dimming. they were completely out, but the flourescent displays were on and WOULD dim.
I also lost all chime functions.
now I checked codes and had a B334 and B335, Loss of Serial Data Communications and Loss of Secondary (ECCP) Communication. (electronic climate control panel).
Anyways....
finally my question, I think my PCM is bad, however, I have a spare from the same model car, and the two IC's in it have identical numbers as the old one.
can I just swap the pcm out with the other one? I sure don't want to mess it up. BTW I also have a spare BCM, but the numbers are different. and the PCM smelled burnt but not the BCM.
Thanks for any info guys, I lurk around here, just don't post much.
ps I have pics of computers but couldn't figure out how to upload, I will work on that!

Yes, PCMs should be good with being swapped with same numbers etc.

To add pictures, click the box with the mountains in it next to the happy face in the top of the editor box.

There's no programming needed for any OBD I vehicles.

Thanks, much appreciated.
how about the BCM? The chip inside it has a completely different number on it.
my thought process was it's the PCM because it smelled burnt, but the BCM controls most of the functions I mentioned.
any opinion if I should replace one before the other?
The two chips on the left are the ones in the PCM in the car now. The ones on the right are the spares I have.
https://cimg2.ibsrv.net/gimg/www.gmf...331640814e.jpg

BCM
One long chip in each. 7170 on left, 9709 on right.

https://cimg2.ibsrv.net/gimg/www.gmf...d5653749f7.jpg
https://cimg3.ibsrv.net/gimg/www.gmf...5fdef2e905.jpg

I concur the BCM is most likely suspect for your issues. A Tech1 would be nice. Actually any decent scan tool could look at the data line. That would tell you a lot.

I didn't know I could use a scan tool on an OBD1 car. I have a Bosch scan tool. I'll give it a try.
I did put the spare PCM in the car and nothing changed.
Then I took it back out and put the original back in and took out the BCM and put the spare one in and it said Electrical Problems on the display and still no dash lights. so I put the original BCM back in and the electrical problem display went away. so i guess I'm back to square one. I'll put the scan tool on it tommorrow and take a look.
Then I guess it's on to old fashioned step by step troubleshooting. (I have a FSM).
Thanks for the help, I'll post what I find.

GM has datastream in yours and most other OBD I vehicles.
I'm not familiar with that tool. If it can read the BCM you'll be good.
Do you have the paper manual produced by Helm, Inc.?

I think it's a GM publication FSM. about a million pages long! indispensable.
https://cimg1.ibsrv.net/gimg/www.gmf...adacb325f5.jpg

update on my electrical problems.
Sorry it took so long but I just found the problems this past week. I have been restoring the car and took the interior out and carpet and redid them. Got them back together and took the door panels off and did them and all the switches etc.
So I started trouble shooting the door lock problem first. I had put a remote start, keyless entry unit in it years ago and thought it might be causing the problem so I unhooked everything. still same I started tracing more circuits and basically found out the OEM keyless entry was causing it. luckily I had a spare from junkyard and it fixed the problem.
Started troubleshooting the incandescent dimming problem. the 12v circuit was shorted to ground. so i started removing anything that had bulbs in it. IP, headlight switch, climate control, driver information center and still no luck,
Starting to get really frustrated!! Then I realized I forgot the glove box and ashtray. I had removed both for restoring. found the wire for the ashtray bulb touching the ground side of thee plug! put a bulb in it and it fixed the problem.
Sometimes this makes me wonder how good a mechanic I am!!! Anyway, even though it took me until now, I thought I would let you all know since I get so much help here. I will post pics of some of my work soon.