B1428

Step 1: Perform visual inspection of instrument cluster seat belt warning lamp during bulb test mode (key on, all lamps illuminate). Verify if seat belt lamp illuminates during bulb check. If lamp does not light during bulb test, proceed to lamp circuit diagnosis.

Step 2: Access instrument cluster connectors and inspect for corrosion, bent pins, or moisture intrusion. Using a digital multimeter, backprobe the seat belt lamp circuit wire at the instrument cluster connector (typically a 12V switched signal from BCM) and verify voltage present when ignition is on.

Step 3: Disconnect instrument cluster and measure resistance of seat belt lamp circuit from cluster connector back to BCM connector (should be less than 5 ohms). Check for short to ground (should show infinite resistance to ground) and short to power (no voltage present with ignition off).

Step 4: If wiring tests pass, remove instrument cluster and inspect bulb socket or LED connections for damage, corrosion, or loose solder joints. Test lamp circuit driver output at BCM connector if cluster is confirmed good.

Step 5: If all physical components test good, perform BCM functional tests using enhanced diagnostics to command seat belt lamp on/off. Clear codes and verify repair by cycling ignition and confirming seat belt lamp operates normally during startup sequence.