P1631 BUICK, CADILLAC, CHEVROLET, GMC: IMMOBILIZER FUEL ACTIVATION SIGNAL IS NOT CORRECT.
POST UPDATED IN May, 2023
P1631 BUICK, CADILLAC, CHEVROLET, GMC: IMMOBILIZER FUEL ACTIVATION SIGNAL IS NOT CORRECT.
The immobilizer belongs to your vehicle’s security system, it avoids the engine starts unless the transponder key is present. When the key is inserted into the ignition switch, this transmits an electronic code to the vehicle. The engine will only start if the smart key fob matches the immobilizer code.
The BCM (Body Control Module) often communicates with the ECM (Engine Control Module) by sending a security code through a serial data circuit. After this, the ECM sends a challenge to the BCM. Both controllers make some calculations on this challenge. If the calculated response of the BCM is equal to the calculation performed by the ECM, the vehicle may start.
The P1631 OBDII diagnostic code setting occurs when the security code received by the Engine Control Module from the Body Control Module is wrong.
Reasons to set the P1631 OBD2 fault code:
To troubleshoot DTC P1631 OBDII, try this: