Low Beam Headlights Will Not Turn Off
NOTE:
After making any repairs, perform BODY CONTROL MODULES SYSTEM VERIFICATION TEST
under VERIFICATION TESTS.
- Turn ignition off. Connect scan tool to Data Link Connector (DLC). Using scan tool, retrieve Body Control Module (BCM) Diagnostic Trouble Codes (DTC). If scan tool displays HEADLIGHT SWITCH INPUT FAILURE, perform HEADLIGHT SWITCH INPUT FAILURE test. If any other DTCs exist, repair those before proceeding. See DIAGNOSTIC TROUBLE CODE IDENTIFICATION table under SELF-DIAGNOSTIC SYSTEM. If no DTCs exist, go to next step.
- Ensure headlight switch is off. Using scan tool, read HEADLIGHT SWITCH voltage. If voltage is 4.3-4.8 volts, go to next step. If voltage is not 4.3-4.8 volts, replace headlight switch.
- Turn ignition off. Remove low beam relay from junction block. See Figure . If low beams turn off, leave low beam relay removed, and go to next step. If low beams do not turn off, install low beam relay, and repair short to voltage in low beam relay output circuit between low beam relay and headlights. See HEADLIGHT SYSTEMS article.
- Substitute known-good low beam relay. If low beams do not operate properly, remove low beam relay, and go to next step. If low beams operate properly, replace low beam relay.
- Ensure ignition is off. Remove Body Control Module (BCM) from back of junction block. Measure resistance between ground and terminal No. 14 at BCM connector on back of junction block. See Figure . If resistance is less than 5 ohms, replace junction block. If resistance is 5 ohms or more, leave low beam relay and BCM removed, and go to next step.
- Measure resistance between terminal No. 14 and each other terminal at BCM connector on back of junction block. If any resistance is less than 5 ohms, replace junction block. If all resistances are 5 ohms or more, replace BCM.