Test No. 8: Flash High Beam Headlight Feature Does Not Operate

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 flash high beam headlight feature. See HEADLIGHT CONTROL SWITCH under REMOVAL & INSTALLATION.
Check wiring harness and electrical connectors between headlight control switch and body Electronic Control Unit (ECU), and between headlight control switch and headlight. See WIRING DIAGRAMS in HEADLIGHT SYSTEMS article or DAYTIME RUNNING LIGHTS article. Body ECU is located at driver'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 flash high beam headlight feature.
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 flash high beam headlight feature.
Replace body ECU with a known-good body ECU and recheck flash high beam headlight feature. If flash high beam headlight feature operates properly, original body ECU was defective. If flash high beam headlight feature still does not operate properly, check wiring harness and electrical connectors for body ECU, headlights and headlight control switch for intermittent problem. See WIRING DIAGRAMS in HEADLIGHT SYSTEMS article or DAYTIME RUNNING LIGHTS article. Repair wiring harness or electrical connector as necessary.