Section 8 (Anti-Theft System): Operation

WARNING: This page is about a different car, the 1998 Isuzu Hombre. However, it is still accessible from the selected car via links, so may be relevant.

When mechanical key turns the PassLock(R) lock cylinder, a Resistance Code (R-Code), is created by a rotating magnet turning past a stationary Hall Effect sensor. R-Code is sent to the BCM. The module determines the validity of the R-Code within a preset time window, then sends a coded password over the Class 2 serial data line to the Powertrain Control Module (PCM)/Vehicle Control Module (VCM), which then allows the fuel injectors to operate normally. See Fig 1 .

If BCM sends a password that is different than learned password in PCM/VCM, PCM/VCM will go into NO START MODE. During this mode, the fuel injectors will be shut off for 10 minutes and SECURITY light will stay on. Vehicle may crank and temporarily start, but will soon stall due to fuel shut-off. If a large magnet is placed near PassLock(R) sensor, a tamper signal will be sent to BCM. System is continually self diagnosing certain functions. If a malfunction exists, system will store a DTC. BCM does not illuminate MIL light. If a PassLock(R) DTC exists, BCM illuminates SECURITY indicator light.

Fig 1: Anti-Theft System Operation

Courtesy of ISUZU MOTOR CO.