Good day everyone, I have swapped out my ECM with one from the parts yard. The Service numbers are the same I just swapped out the module inside the unit. The truck cranks and starts up but then shuts down.
Truck ran fine before the swap, I did the swap because my AC would always run. I traced and troubleshooted the circuit and the wiring is good, so I purchased another ECM. When I installed the new ECM and turned the key to the run position, the AC compressor was not engaged until I turned the switch on, compressor engaged as it should. switch off ac was off, the ecm was bad or damaged somehow. . How do I get this replacement ECM to work for my truck? 1998 Silverado C2500, 5.7 Vortec, automatic

Thank you

 

The theft deterrent system is activating - allowing a start and shutting off is exactly what it does.

Most likely you need to perform the Passlock relearn, but to be sure, check for codes first. Codes can be stored even without the CEL being on. If it’s a Passlock issue, a corresponding code will be set.

 

A little known problem, if you substitute an nonprogrammed ECM to a vehicle, the anti theft system will not recognize the replacement ECM, PLUS the switch has confused the anti theft system and now the original ECM will no longer be recognized

Now a shop, dealership or certified locksmith has to be utilized to reprogram the ECM to the individual vehicle.
In order to do this, access to security info, is necessary and the person/location has to have a security clearance to access it.

Supposedly, this is all to prevent anyone from stealing your vehicle.

 

Where did you find/learn this information?

 

Hi everyone, here is where I am. I located a company that comes to you and will "Flash" you ECM and reinstall the factory software and then all the updates that were put out for that year model, they also relearned the security system. The truck started right up and runs better then it did before. I mean really better!! thank you for all the help and advise provided.

 

Hi Gumby,
ATG,,,,,,,,,,,,,,Automotive training group manuals. located in California. Lots of good stuff in their manuals.
They also hold seminars which you can attend. Of course they aren't free, but worth every penny.