2006 GMC Sierra. Flash the PCM, truck cranks/starts fine.

I then plugged in a different PCM, flashed the same tune to that PCM - truck crank/starts no problem

I re-installed the ORIGINAL PCM (the first one I flashed, which worked fine), but now when you go to start it, nothing happens. Lights/gauges/etc all come on w/ Key ON and the headlights shut off when you go to crank, but nothing happens - no click from the starter relay or anything. I swapped back the other PCM that started up, and it is still doing the same thing - wont crank.

Is there some sort of security feature? It does not have power door locks. Also on both PCMs they were flashed to remove VATS.

Maybe something needs to be reset? I'm lost at this point. I've tried disconnecting/connecting the negative side of the battery numerous times, still wont crank.

Also, the OBD2 port is getting power, but it will not connect to HPTuners.

Battery is charged fully. Played around with the wiring harness while key was set to "start" to see if there was a loose wire, but no luck.

Any help would be much appreciated.. Thanks

 

You may have triggered the security feature.

Steps

Make sure the battery if fully charged because this procedure may take up to 30 minutes and you cannot start the vehicle during this time. The instrument panel cluster (IPC). BCM and PCM must be in working order and the Passkey system repaired

1. Turn the key to ON and attempt to start the engine and release the key to the ON position.

2. The SECURITY light will illuminate. Wait 10 minutes until it turns off.

3. Turn the key to OFF for 10 seconds.

4. Turn the key to ON and attempt to start the engine. If it starts and run, the system has reset. If it doesn’t start or run and release the key to the ON position and complete the rest of the steps.

5. The SECURITY light will illuminate. Wait 10 minutes until it turns off.

6. Turn the key to OFF and wait 10 seconds.

7. Turn the key to ON and attempt to start the engine and release the key to the ON position.

8. The SECURITY light will illuminate. Wait 10 minutes until it turns off.

9. Turn the key to OFF and wait 10 seconds.

10. Start the engine

 

The 2 highlighted descriptions above point to a connection issue. Make sure you did not bend one of the pins on the original PCM. Likely its not getting a ground signal somewhere.

 

Does it say interface was detected but cannot connect to vehicle, something like that?

 

Check the PCM 1, PCM B, and IGN 0 Fuses.