Test No. 15: Driver's Seat Belt Warning Light Does Not Turn Off

Seat belt buckle switch is located near the bottom of seat belt assembly on driver's seat belt assembly. When ignition is on and seat belt is disconnected, the body Electronic Control Unit (ECU) delivers a signal to flash the driver's seat belt warning light and sound a buzzer. Continuity should exist between electrical terminals for seat belt buckle switch with seat belt unfastened (ON position) and no continuity should exist with seat belt fastened (OFF position). Verify that seat belt buckle switch is operating properly. If seat belt buckle switch is operating properly, go to next step. If seat belt buckle switch not operating properly, replace seat belt buckle switch and recheck driver's seat belt warning light operation.
Check wiring harness and electrical connectors between seat belt buckle switch on driver's seat belt and body ECU, and between seat buckle switch and body ground. See WIRING DIAGRAMS in WARNING SYSTEMS article. Seat belt buckle switch may also be referred to as buckle switch. Body ECU is located at driver's side of instrument panel on the fuse/relay box and contains an 18-pin and 20-pin electrical connector. See Figure. If wiring harness and electrical connector are okay, go to next step. If wiring harness or electrical are defective, repair as necessary and recheck driver's seat belt warning light operation.
Check body ECU for proper voltage and input signals. See BODY ELECTRONIC CONTROL UNIT under PIN VOLTAGE TESTS. If proper voltage and input signals exist, go to next step. If proper voltage and input signals do not exist, repair as necessary and recheck driver's seat belt warning light operation.
Replace body ECU with a known-good body ECU and recheck driver's seat belt warning light operation. If driver's seat belt warning light operates properly, original body ECU was defective. If driver's seat belt warning light still does not operate properly, check wiring harness and electrical connectors for body ECU, seat belt buckle switch and driver's seat belt warning light for an intermittent problem. See WIRING DIAGRAMS in WARNING SYSTEMS article. Repair wiring harness or electrical connector as necessary.