PCM on a 2000 GAGT questions [Archive] - GrandAmGT.com Forum

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76TA01GAGT
01-24-2010, 09:49 AM
I have a 2000 and 2001 GAGT (son and daughters cars). Our code reader will read her car with no issue and even give the VIN. His, the 2000 will not read the sensors or give the VIN, is this because its a 2000 or because its a bad PCM? Also, when you change the PCM, what is the procedure for re-starting, can it be done at home? Thanks for any help/ guidence or direction to a thread that has the answewr (I couldnt find them just now).

KhellendrosxS
01-24-2010, 11:25 AM
The PCM diagnostic port (OBD 2 for both cars) receives power from the cigarette lighter circuit. If this fuse is blown then you will not be able to read the PCM.

I believe that particular fuse is under the hood in the big black box that has relays in it. Check it out and change it if it is blown.

If you do have to change out the PCM-which isnt likely to be the case unless you hooked the battery wires up wrong and sent power through the ground, bypassing the fuse protection-then you need to match up the service number on the one you have with the replacement. A quick check of the PCM compatablitiy chart shows that all 2000's and some 2001's will serve as replacements. You may be able to start the car following a completion of the Passlock procedure explained in the manual. If you dont have one it is available here by searching. You WILL have to take it to the dealer to have something called a "Case Learn" procedure done after the PCM is changed. This cannot be accomplished by your handheld scanner. It is only possible using HPTuners, DHP Powrtuner, or a Tech II (available at the dealership). I believe the cost for that is around $50.


What leads you to believe the PCM is bad?

AaronGTR
01-24-2010, 12:01 PM
^What Chris said. The pcm is exactly the same between the two years. Only reason you wouldn't be able to read one is either that fuse is blown and the OBD port isn't getting power, or it's a software compatibility issue with your scanner.


Either way, if you did have to change the pcm you'd just have to get one with the same service number. If you got one from the same make/year then you could switch it out yourself, and the car would start after doing the security learn procedure. You'd have to take it to the dealership though or someone with a tuner to get the CASE learn done and also to get the VIN updated and turn the security off, or it might not start the second time. The security procedure is built into the pcm's basically so you can start it once and get it to the dealership to get fixed. :thumbs:

76TA01GAGT
01-24-2010, 01:23 PM
I am pretty sure its not the scanner as it will read the 2001 with no problem. As for the fuse, it looks good and the cigarette lighter works. We bought this car with a rod knock. Since we didnt want to grenade it (the engine) we only started it long enough to get it on the trailer and off (it did have just about every light possible lit up at that time). After the re-build we hooked everything back up and it started immediatly and sounds great. But the SVS (not SES), ABS and Traction controls lights are still on. I am planning the review of the wheel sensors as outlined elsewhere here to see if thats whats going on with those lights. My issues with the PCM is not being able to see the VIN and have it tell me the sensors are okay, it does give me live information when the car is running, so maybe i dont need to worry about it. After reading here I am somewhat suprised that it started so easily after we completly re-built it (30 over, new everything, including cam). Looking back, buying one with a bad engine, that I didnt know the history on, might not have been a great idea! Keep the thoughts and information coming, we appreciate it all!

76TA01GAGT
01-24-2010, 01:24 PM
One other question, did a lot of people not set up the theft lock when new? Both our cars were bought used and so far when i have diconnected the batteries and re-attached we havent had a problem...........

lastryghts
01-24-2010, 01:33 PM
I'm pretty sure are stock radeos get a code from the BCM and don't need a code manually entered. This is why if you install a new GM radio you need to go to the dealer and have them "unlock" it.

76TA01GAGT
01-24-2010, 01:39 PM
Hmm, this one had an aftermarket radio already in when we got it, would that cause the code reader to not be able to report the VIN?

KhellendrosxS
01-26-2010, 08:39 PM
Hmm, this one had an aftermarket radio already in when we got it, would that cause the code reader to not be able to report the VIN?

No. Ill Ill take a stab at the rest of the questions above in the morning once Ive gotten some sleep. Stupid conventions are killing me.;crap

76TA01GAGT
01-27-2010, 06:44 AM
Thanks for any help!

KhellendrosxS
01-27-2010, 10:34 AM
I am pretty sure its not the scanner as it will read the 2001 with no problem. As for the fuse, it looks good and the cigarette lighter works. We bought this car with a rod knock. Since we didnt want to grenade it (the engine) we only started it long enough to get it on the trailer and off (it did have just about every light possible lit up at that time). After the re-build we hooked everything back up and it started immediatly and sounds great. But the SVS (not SES), ABS and Traction controls lights are still on. I am planning the review of the wheel sensors as outlined elsewhere here to see if thats whats going on with those lights. My issues with the PCM is not being able to see the VIN and have it tell me the sensors are okay, it does give me live information when the car is running, so maybe i dont need to worry about it. After reading here I am somewhat suprised that it started so easily after we completly re-built it (30 over, new everything, including cam). Looking back, buying one with a bad engine, that I didnt know the history on, might not have been a great idea! Keep the thoughts and information coming, we appreciate it all!

I think youre worried about too much by not seeing the VIN. It really isnt necessary for any diagnostics. The fact that your scanner is recieving information when the car is running is a good thing and means that the PCM port is working properly. You wont see any codes if there is nothing wrong (your SES light is off).

The S"V"S light refers to a problem with something not related to the mechanical workings of the car. Chances are you have a blown headlight or tail light. These are the most common trippers of the SVS. As for the ABS and Trac light you are right on the money to suspect the hub assembly.

One other question, did a lot of people not set up the theft lock when new? Both our cars were bought used and so far when i have diconnected the batteries and re-attached we havent had a problem...........

The theft lock is integrated in the key cylinder and BCM. There is no set up procedure. What will happen over time is either the tumblers get worn out or the key itself will get worn out and cause the SECURITY light to start causing Passlock goofyness. Heavy keychains with lots of items dangling on them seem to also cause the cylinder to wear out faster so if your son or daughter have things like flashlights, knives, or do-dads you might want to tell them to take them off as a new key cylinder is not very cheap and a PITA to replace.

Every time I work on my car I disconnect the negative cable and so far have never had a problem with the theft system when I try to start the car. What will happen if the battery is disconnected for more than 10 minutes is to clear out all the stored codes in the PCM. This is useful for people that fix a problem but dont have a scanner to clear the codes once the repair is done.

Now, if there is still something wrong the SES light will come back on eventually but may not right away.


Best of luck with the cars!

76TA01GAGT
01-28-2010, 08:31 AM
Wow, thanks for the information. I think the next step is the hub assembly, in my thinking, I should check the assembly for resistance out of the box, my other though is to pop the tire off and hook the assembly to the wiring on the car and see what it does to the ABS and Trac light, sound like a good plan of attack? For now I will ignore the lack of VIN..............