Well I'm back at it with this car again. I still have not started the damn thing. I got a pass thru pro 3 from snap on and order a 2 day pass through ac Delco. Then hooked it up to the car and tried to perform the security relearn but got no where. The program did not find the ecu at all. While looking under the dash I did find I think is an aftermarket alarm spliced into the car. At least I think it's aftermarket. Do any of you guys have this set up under you dash? because I'm thinking about removing it. I know you guys have told me it's a security problem but the security relearn program didn't work. I willing to try anything right about now I'm even think about buying another Monte and swapping all the harness dash to engine. Any suggestions on the next step? It's been over 3 yrs since I drove it. Alarm?
Snap on pass thru pro 3. No communication with the ecm

 

That is definitely an aftermarket rig. And that brings a good point. If that is an aftermarket remote start, one of the modules is going to do something with passlock to bypass it. I would wonder if that module is interfering with a PCM re-learn process.

For the record, on my Grand Am, I installed a keyless entry system in it. It uses the same PCM hardware as my Monte (just a different program). I have had to replace the Grand Am PCM before and do the relearn without issue and that is with the remote start and passlock bypass module.

But I am more concerned that your Snap-On tool could not connect to the PCM. That clearly states there is a break in communication between the diag port under the dash back to the PCM. You might need to check the wiring. Such as, at the diagnostic port is two grounds, a 12v pin and a data wire. Make sure ground and power are good and then check if the data pin has connectivity to the PCM.