Immobilizer System

WARNING: This page is about a different car, the 1997 Cadillac Catera. However, it is still accessible from the selected car via links, so may be relevant.

Check for proper installation of aftermarket electronic equipment.
Using a DVOM, check for battery voltage at theft deterrent module terminal No. 9. See Fig 1 .
Turn ignition switch to ON position. Check for battery voltage at theft deterrent module terminal No. 5. See Fig 1 .
Check Black ground wire between theft deterrent terminal No. 4 and chassis ground located at left front of engine compartment.
Check for damaged and/or poor wire connections at connector terminals.
Check theft deterrent module for Diagnostic Trouble Codes (DTCs). If DTC is intermittent, check DTC while wiggling wiring and connectors.

Fig 1: Identifying Theft Deterrent Module Connector Terminals

Courtesy of GENERAL MOTORS CORP.