Diagnostic Aids

Check for poor connection at the BCM. Inspect the harness connectors for backed out terminals, improper terminal mating, broken connector locks, improperly formed or damaged terminals and poor terminal-to-wire connection (terminal crimped over wire insulation and not conductors).
Inspect wiring harness for damage. Check for broken or chafed insulation.
Check for poor connection at the passlock sensor.
If fault is suspected to be intermittent, wiggling harness wiring may help in locating fault.

Fig 1: Security System Data Incorrect But Valid Chart

Courtesy of GENERAL MOTORS CORP.