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DTC B1970: Exterior Light Power Fault: Testing

  1. Perform lighting system diagnostic system check. See LIGHTING SYSTEM DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
  2. Remove low beam relay from relay box located under instrument panel. See Figure . Connect scan tool to DLC. Turn ignition on. Select EXTERIOR LAMP output in data display on scan tool. Ensure exterior lamp output is displayed as ON. If exterior lamp output is not displayed as ON, cover light sensor located in center of dash. Using a DVOM connected to good ground, measure voltage at low beam relay terminal No. 3 (Red/White wire) in relay box. See WIRING DIAGRAMS  . If 10-12 volts exist, go to next step. If 10-12 volts does not exist, go to step  4 .
  3. Reinstall low beam relay. Using scan tool, clear BCM DTCs. Retest for DTC B1970. If DTC B1970 is set as a current code, go to step  5 . If DTC B1970 is not set as a current code, go to DIAGNOSTIC AIDS  .
  4. Turn ignition off. Disconnect BCM 24-pin connector C1. Using DVOM, test Red/White wire between BCM 24-pin connector C1 terminal B10 and each relay for short to ground. See WIRING DIAGRAMS  . After fault is located and repaired, go to step  6 .
  5. Replace BCM. See BODY CONTROL MODULE (BCM)  under REMOVAL & INSTALLATION. Reprogram BCM. See PROGRAMMING  . After replacement, go to next step.
  6. Reconnect all disconnected components and connectors. Using scan tool, clear BCM DTCs. Verify BCM operation by commanding headlights and interior lights ON and cycle ignition locks. If DTC B1970 sets, go to step  2 . If DTC B1970 does not set, system is okay.
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