Test No. 7: Headlight Does Not Operate With Engine Running & Headlight Switch In Off Position
- Check charging system to verify proper operation of generator. See appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS. If charging system is not operating properly, repair charging system as necessary and recheck headlight operation. If charging system is operating properly, check wiring harness and electrical connectors for inoperative headlight. See WIRING DIAGRAMS in DAYTIME RUNNING LIGHTS article. If wiring harness and electrical connector are okay, go to next step. If wiring harness or electrical are defective, repair as necessary and recheck headlight operation.
- Check body Electronic Control Unit (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 headlight operation.
- Replace body ECU with a known-good body ECU and recheck headlight operation. If headlight operates properly, original body ECU was defective. If headlight still does not operate properly, check wiring harness and electrical connectors for body ECU for an intermittent problem. See WIRING DIAGRAMS in DAYTIME RUNNING LIGHTS article. Repair wiring harness or electrical connector as necessary.