2kvert,

You cannot just put another PCM in the car without being able to reprogram it. That is because the BCM and the PCM have an "agreed upon" password that the BCM sends when you try to start the car. Without being able to reprogram the "new" PCM, it will not recognize the "old" BCM password. As the service manual says :

"If the BCM and PCM are not properly programmed together, the vehicle will exhibit a no start condition and the PCM will store a DTC P1631"

Try the suggestions we've given you ...

1) New battery

2) Check fuses (especially those providing PCM power)

3) Check for loose wires or bare (grounded) wires

If those don't get ya going, you will need the services of someone with a Tech2 scan tool and access to GM's Techline system, which is basically a dealer. The Techline access is needed to get the correct software for your PCM based on your vehicle's VIN. Best of luck, Steve

 

That is good information. That is exactly what your IPC should do when it don't hear from your PCM. With that cleared up lets focus on the PCM. If you have a C5 PCM you can borrow that would be a good place to start. I think any C5 PCM from 99 to 04 should work for your test, 97 and 98 will NOT work. It will not run the car without flashing the correct OS in the PCM and programming it for our car but it should allow you to test communications between the IPC and PCM. Your best matched PCM will be a PCM from a 2001 or 2002 manual car if you have one of those you can borrow. You should only need to hook up the PCM connector C1, which should be the blue connector. Remove both plugs from your PCM and only hook up connector C1 the blue connector to the borrowed PCM. Then don't try to start the car, just check your codes and see if the IPC can talk to the PCM, it will set all kinds of codes, but communications is all your worried about right now. If it can communicate then hook everything back to your PCM and make sure it still don't work, then you will know it is a bad PCM. If you can't communicate with the borrowed PCM then use an ohm meter to check your serial data wire. You will want to check for continuity between pin 58 (dark green wire) of the blue PCM C1 connector to the star buss connectors located just to the left of the BCM inside the right foot well. The star buss connectors are the two flat plugs just to the left of the BCM, they will have a jumper plug plugged into them. No wires comes out the top of the jumper plug. It will be best to leave the star buss jumper plugs in place while checking for continuity. Unhook the battery when doing this as other devices will be trying to pull the data buss up to 7.5VDC and you don't want that in your ohm meter. You should be able to slide a paper clip up from the back of the plugs beside the wire to make contact. If you have to pull the jumpers to get connected simply check all the wires in both connectors, one of them should have continuity to pin 58 of the C1 PCM connector. If you can't find continuity then I can get you a better wiring diagram to start tracing wires with. You can find a PCM pin out and connector diagram for all C5 PCMs here. While you have your PCM disconnected be sure to check the connections very good for corrosion. It is a common problem for these PCM connections to become corroded. I don't think you will find a wiring problem since this all started with a dead battery. It is hard to say what caused the problem but if a helper or someone connected the cables or charger backwards it could cause problems like this as well as blowing fuses, you have checked all fuses, correct? Hope no one reversed the cables is not the case, that can do a lot of damage.

Let us know what you find!

 

I checked and rechecked the fuses underhood and in car. All check fine. I went ahead and put a new battery in for good measure and will have it sitting at the dealership first thing Thursday morning. That should be fun. Again, thanks for all the help and advice and I will post results as soon as I have them. I think I will try your idea on the pcm swap just to satisfy my curiosity.

 

It's running! Picked it up from the dealership yesterday. The mechanic told me that 2 wires had been broken somehow right around the connectors attached to the inner fender at the battery. He said whichever wires it was were important because he couldn't get the TECH 2 to communicate with hardly any system. Got it fixed so I can finally rest. Again, thanks to all who gave me advice. You guys are extremely helpful even when the end result is the dealership!

 

So was thi an area you working working on or near where the 2 wires were broken? Im curious if they were actually broken at the connector portion or in the actual wire as being pinched or cut.

 

No I was not working in that area when it happened. The mechanic and I assumed the wires had been broken previously and when I took the battery out of the car, I probably snagged them and pulled them apart the rest of the way. The wires were not at the connector, they were in the harness about 8 or 10 inches away from the connector towards the underhood electrical center.