Chevy Cobalt Forum banner
1 - 4 of 4 Posts

·
Registered
Joined
·
651 Posts
Discussion Starter · #1 ·
Well besides the bad shift solenoids I was dealing with starting at the beginning of October, I now have a bad TCM. It has the dreaded loss of ground. It is currently in working order since installing an external ground strap to the TCM casing and run to the strut tower.

I assume this fix will not last long and am planning on having to replace the TCM. There’s several options at hand I’ve found. Used is of course initially the cheapest route. But will the used TCM work correctly? Or will it happen to be locked and not able to be programmed? That’s my biggest worry going with a used unit. Or it will work for a short time and crap out like my original one. Used ones are $40. And I probably need to find one that is for my ‘06 with the same options. My car has almost every electrical option besides a sunroof, amplified stereo, and power seat.

Other options are refurbished or remanufactured units. On Amazon there’s a company called Flashmasters. For about $80 they appear to sell you a good TCM VIN matched to be ready to install into your car. Basically a “plug & play” TCM or other module that you’re buying. Sounds good, but almost too good. I don’t want to potentially waste money here.

Dorman sells a TCM, has a limited lifetime warranty. But it has to be programmed. I looked and it works with many GM cars and trucks, so programming is pretty much a have to do thing here. These are sold for $135. I’m wondering if they have fixed what goes wrong internally or what if any improvements are made. These are readily available online and locally at the parts stores.

Other mechanics that I’ve asked opinions on the TCM are to get the on the dealership sells. Probably because it will likely work with no problems. Or be able to be programmed more easily. I don’t really know why the genuine GM part is highly recommended in this case. I do know I find the AC Delco stuff is just best when I’ve used it on the Cobalt replacing various things. The TCM at the Chevy dealership is about $130. Meaning I’m really only saving $30-$50 if I get an aftermarket unit. Maybe I’ll spend more with an aftermarket too.

I’m probably going to spend the money and get the OEM part though as the cost savings are just not much. I can find some TCMs for about $90 online from Cardone and Dorman. But are they the AC Delco quality? Who knows.

Programming is going to be $125 according to the neighboring mechanic that has access to the software and programming subscription. He’s being nice enough not to charge me additional labor as I have helped him by doing alignments on vehicles they have worked on and get him in and out quickly every time. It pays to be good to the neighboring shops. I don’t need help too often, but when I do, I usually don’t have to pay a lot.

I haven’t made up my mind yet. I kind of want to try a used TCM. I really want to see what it'll do since there’s no concrete evidence that I can find that they will or won’t work as a plug and play part. I known it needs to be from a car of the same year or at least 05-06 cars. And probably the same options. I suppose it can’t really mess anything up except that I’d waste $40 to basically do a coil flip where it’s a 50/50 chance.

The fact the dealership has one in stock and I can just go pick it up is probably reason enough I’ll get the OEM part. I know it’ll work after it’s programmed. And I believe it comes with a warranty of 2 years and unlimited mileage. Fairly standard with AC Delco stuff.

Have any of you had luck with putting a used TCM in your Cobalt? I always assumed it still has to be VIN matched by programming it after installation. But perhaps if I pull a TCM from an 05-06 sedan it’ll work fine. Most of the two years I can find are coupe models so that’s a no go for direct use, I assume.
 

·
Say What again!
Joined
·
6,422 Posts
I can't imagine the TCMs are any different between coupe or sedans...
 

·
Registered
Joined
·
651 Posts
Discussion Starter · #3 ·
Well I was under the impression that if I install a used one it had to be the same model and all the same options. Perhaps that would be the case with a BCM or PCM. There’s no way for me to test a TCM from the junkyard until I have it installed on my car. Which is kind of a $40 roll of the dice.

Kind of want to know about trying a used one since they’re so cheap. But I had a bad experience buying a used PCM in the past. Has to end up buying two for my old Mercedes. One crapped out and luckily at the time there was quite a few of the old S-Class models in the yard.

I have to wonder are there any programming differences between the 05-06 compared to the later models. Because the 2.2 models have very different PCMs in the later models.

The transmission shifting has been acting up again so I’ll probably need to get the TCM soon. It did the 4th to 1st downshift which is not great for the engine. Seems to only do it during hard acceleration. I also noticed a few things not working. Automatic locks because of TCM confused about shifter position, also traction control is non existent. Shift lock solenoid operates in drive when the brake is applied, so TCM doesn’t see the shifter in drive position, as if it’s still in park. But drives normally otherwise most of the time.
 

·
Registered
Joined
·
651 Posts
Discussion Starter · #4 ·
So I installed a TCM from an ‘05 LS sedan. Works fine. Or I should say it was working fine. Same symptoms came back after 5 drives. I have a feeling it may be something to do with the connector. I’m going to go ahead and install the internal harness inside the transmission. And also clean and press the wires back into the harness at the module. At least I didn’t waste the $255 I would have spent on a new module and programming. Hopefully this works.
 
1 - 4 of 4 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top