DTC P1631: Theft Deterrent System - Password Incorrect: Description

WARNING: This page is about a different car, the 2002 Saturn LW200, 2002 Saturn L200, and 2002 Saturn L100. However, it is still accessible from the selected car via links, so may be relevant.

Passlock(R) system is designed to prevent vehicle theft by allowing PCM to disable fuel injectors unless correct key (voltage) code from Passlock(R) sensor via mechanical key is correct. Passlock(R) system utilizes 4 components: lock cylinder, Passlock(R) sensor, BCM and PCM. When engine is cranked, BCM will look for a password from Passlock(R) sensor. If password is not received within a certain amount of time or is incorrect, BCM will send a "fuel disable password" to PCM over Class II link. SECURITY light will flash and engine will not be allowed to start. If BCM receives correct password from Passlock(R) sensor that it has stored in memory, it will send it over Class II link to PCM. If PCM Passlock(R) password it has stored in memory does not match BCM password, or if PCM receives an undecided password from BCM, it will allow engine to start, then stall within 4 seconds. SECURITY light will flash for 10 minutes if PCM receives an undecided, incorrect or fuel disable password. If password to PCM is correct, engine will operate normally. Password is sent continuously by BCM to PCM during run mode. If password becomes lost or incorrect during drive cycle, vehicle will be allowed to start on succeeding ignition cycles without the aid of Passlock(R) and SECURITY light will be on steady. This mode is called fail enable mode.