Preliminary Checks

In order to correctly diagnose a no-start, battery voltage must be greater than 11 volts and engine must be cranking at normal cranking speed (greater than 200 RPM). Fuel level and fuel quality in fuel tank should be checked (do not rely on fuel gauge). When engine is cranked, BCM will check the password from the PassLock® sensor. If password is not received within a certain amount of time or does not match the BCM password, BCM will send a "fuel disable password" to ECM over the CAN bus. The SECURITY indicator light will flash and engine will not start. If the passwords match, BCM will send the password over the CAN bus to ECM. If ECM password does not match the BCM password, or if ECM does not receive a password from BCM, it will allow engine to start and stall within 4 seconds. The SECURITY indicator light will flash for 10 minutes if ECM receives no password, an incorrect password or a disable fuel command. If password to ECM is correct, engine will operate normally.

The password is sent continuously by the BCM to the ECM during run mode. If password becomes lost or incorrect during the drive cycle, vehicle will be allowed to start on succeeding ignition cycles without the aid of PassLock® and the SECURITY indicator light will be on steady. This mode is called fail enable mode.