Test No. 4: Headlights & Taillights Do Not Operate

Check bulbs for headlights and taillights. If bulbs are okay, go to next step. If bulbs are defective, replace bulb and recheck headlight and taillight operation.
Check headlight control switch. See HEADLIGHT CONTROL SWITCH under COMPONENT TESTS. If headlight control switch is okay, go to next step. If headlight control switch is defective, replace headlight control switch and recheck headlight and taillight operation. See HEADLIGHT CONTROL SWITCH under REMOVAL & INSTALLATION.
Check wiring harness and electrical connectors between headlight control switch and passenger's side Junction Block (J/B) Electronic Control Unit (ECU). See WIRING DIAGRAMS in HEADLIGHT SYSTEMS article or DAYTIME RUNNING LIGHTS article. Passenger's side J/B ECU is located at passenger's side of instrument panel. See Figure. If wiring harness and electrical connectors are okay, go to next step. If wiring harness or electrical connector are defective, repair as necessary and recheck headlight and taillight operation.
Check passenger's side J/B ECU for proper voltage and input signals. See PASSENGER'S SIDE JUNCTION BLOCK 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 and taillight operation.
Replace passenger's side J/B ECU with a known-good passenger's side J/B ECU and recheck headlight and taillight operation. If headlights and taillights operate properly, original passenger's side J/B ECU was defective. If headlights and taillights still do not operate properly, check wiring harness and electrical connectors for passenger's side J/B ECU, headlights, taillights and headlight control switch for intermittent problem. See WIRING DIAGRAMS in EXTERIOR LIGHTS article, HEADLIGHT SYSTEMS article or DAYTIME RUNNING LIGHTS article. Repair wiring harness or electrical connector as necessary.