Replaced PCM

[drayner]

Hi, I have a 2001 Chevy Malibu with a 3.1L v6 engine. My pcm (powertrain control module) went bad. At my house, there is a 1999 Oldsmobile Sillouette. I checked online to see if they had the same pcm and they did, so I did the swap. My malibu now runs, but not correctly. Here are the problems running with the new pcm:
1: Fuel/Temp gauges do not work
2: Does not run correctly, it seemed to run ok at first until i pulled it out of the garage, wants to stall, and stalls when i put it in drive

Codes:
P0740 TCC circuit malfunction
P1665 Evaporative emission control system, vent valve solenoid control circuit
P1676 Evaporative emission control system, purge valve solenoid control circuit

I'm assuming the PCM needs a little reprogramming, what I want to know is if i can do this at home. If so, what tools do i need? How difficult is it? I have access to many books on the subject, but i figured i'd ask here first to get some experienced feedback.

Thanks in advance to anyone who can help!!

[drayner]

This forum sucks

[Johnny R]

@ drayner: it appears so do some of the thread starters. We don't owe you.

[Tech II]

No need to get ugly here.......techs can only come here, every so often....

How did you determine that your old PCM was bad?

PCM's can have the same number, and be used in different models and years, but they have to be programmed to the vehicle they are used in......so you can take a PCM out of another vehcle and have it programmed....on the newer vehicles, you can't......they have the VIN # programmed into all the modules, and if you have a module with a different VIN #, the other modules in the car won't be able to communicate with it.....

The only way a PCM can be programmed in your case, is at a GM dealership, or a specialty shop that has the equiptment for programming.....so until that PCM is programmed, those codes have no meaning....

[FishFind]

drayner. It will not run correctly unless you have a Camshaft position sensor relearn. This for for any time that you change a PCM.. The p0740 is a electric issue and you will not have overdrive.
No way can you config the pcm at home unless you have some very pricey tools.

Even though the numbers match I would strongly advise against swapping them. You can get a "new to you" pcm on eBay programmed to you vin. About $100 or less there in 3 days. I have gotten one on there and I can give you the sellers name if you would like.

It may be the same PCM but it is made for a diff car. All the software is incorrect and don't expect it to run good. I am shocked that it started honestly. Like tech2 said a gm dealer can do a re-program or you can buy a new one.

[drayner]

Hey guys, thanks a lot for the feedback, well I took the vehicle to a dealer and they reprogrammed my pcm form me. Ran great on the way home, when I went to start it again, the same problem. This didn't make my day go to well, but a person I know who seems to know a lot told me to check my grounds on the computer. I am gonna try to get to this tomorrow, I will post if it works and if anyone has any other suggestions I would appreciate the help.

[FishFind]

Ok I see that you have the P0740 code. This is your torque converter clutch or overdrive. Most cases it has a bad ground wire and will not allow the car to go into overdrive but in some cases the ground wire can short and keep the TCC in overdrive. If this is the case then the car is always in overdrive and if you go below 40-45mph it will bogg and stall.

the tcc always has +12v along with all the solenoids in the tranny. Overdrive is applied when the PCM tells it to ground. If that wire has a cut and is touching metal somewhere it would explain the stalling.

[Tech II]

Fishfind, I think you are confusing what the TCC does and what overdrive is...overdrive is fourth gear.....when TCC is applied, it is a mechanical linkage of the impeller and the turbine, rich reduces slippage, that a fluid coupling has...... The TCC can apply in 3rd or 4th gear.....

The stalling problem is more likely an engine/driveability problem.....

I am not a transmission guy, but I was told that this could not happen in a 4 speed GM tranny(lockup in 1st gear), because when it downshifts into 1st or second gear, this would open a ciruit that exhausts the lockup pressure.....however, this CAN happen in a 3 speed tranny.....

Three speed trannies were known for stalling when coming to a stop.....it would restart right away, but as soon as you put it in gear it would stall....if you waited about 10 minutes, the solenoid would unstick, and it would be ok to drive, until the tcc sol would apply and stick again....

[FishFind]

It can be done in a 4 speed. I have done it. part of my process in fixing my p0740 was attaching a wire from the ground wire of the tcc solenoid to a toggle switch to the neg terminal of the battery. I was able to apply the tcc "overdrive" in park or any gear as long as that was grounded. If the wire was cut or burned through and touched metal it would do the same effect. The tcc solenoid always has 12v+ once grounded it turns on and stops fluid flow. This is for a PWM valve body. It is supposed to apply in 3-4 gear when working correctly. 45mph it will engage in a chevy, but if a short to ground it will apply no matter what.

[GMCustomerService]

Originally Posted by drayner

Hey guys, thanks a lot for the feedback, well I took the vehicle to a dealer and they reprogrammed my pcm form me. Ran great on the way home, when I went to start it again, the same problem. This didn't make my day go to well, but a person I know who seems to know a lot told me to check my grounds on the computer. I am gonna try to get to this tomorrow, I will post if it works and if anyone has any other suggestions I would appreciate the help.

I'm sorry that the reprogramming done at the dealership didn't resolve the issue for you, drayner. Looking forward to hearing if checking out the grounds has helped, and if I can be of any assistance in following up with your dealership please let me know.

Best,
Sarah
GM Customer Service