I had AEM in my car for the last year and a half while my stock ECU sat in a box. My stock ECU had the injectors re-scaled by vishnu when I ran a piggy back before the AEM. I am now returning my car to stock and plugged in a different same year stock ECU into my car and couldn't get the fuel pump to prime. I recently read that I may have tripped the immobilizer. The problem is that my stock ECU also won't prime the Fuel pump when plugged in. I plugged my AEM back in and the fuel pump can clearly be heard priming. I have never touched the immobilizer code on the ECU itself and never had an issue when I was using it in the past. Did plugging in a different ECU trip the immobilizer so that now my stock ECU also won't work? Is this a dealer fix?

 

NM, problem fixed. Might have been another issue, but forced an OBD2 code reset and all works now.