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DTC B2647: Ambient Light Sensor Circuit Low: 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. Turn ignition off. Connect scan tool to DLC. Turn ignition on, with engine off. Use scan tool to observe ambient light sensor parameter in BCM data display list. If scan tool indicates ambient light sensor input is 0.25-2.5 volts, go to DIAGNOSTIC AIDS  . If scan tool indicates ambient light sensor input is not 0.25-2.5 volts, go to next step.
  3. Turn ignition off. Disconnect ambient light sensor electrical connector. Turn ignition on, with engine off. Use scan tool to observe ambient light sensor parameter in BCM data display list. If scan tool indicates ambient light sensor input is greater than 2.5 volts, go to next step. If scan tool indicates ambient light sensor input is not greater than 2.5 volts, go to step  5 .
  4. Turn ignition off. Connect a 3-amp fused jumper wire between Light Green/Black and Yellow/Black wires of ambient light sensor connector. Turn ignition on, with engine off. Use scan tool to observe ambient light sensor parameter in BCM data display list. If scan tool indicates ambient light sensor input is less than 0.25 volt, go to step  8 . If scan tool indicates ambient light sensor input is not less than 0.25 volt, go to step  6 .
  5. Test Yellow/Black wire between ambient light sensor connector and BCM harness connector C2 terminal B1 for short to ground. See appropriate HEADLIGHT SYSTEMS & DAYTIME RUNNING LIGHTS wiring diagram. After repair, go to step  12 . If fault is not located and condition still exists, go to step  9 .
  6. Test Yellow/Black wire between ambient light sensor connector and BCM harness connector C2 terminal B1 for short to battery voltage. See appropriate HEADLIGHT SYSTEMS & DAYTIME RUNNING LIGHTS wiring diagram. After repair, go to step  12 . If fault is not located and condition still exists, go to next step.
  7. Test Light Green/Black wire between ambient light sensor connector and BCM harness connector C2 terminal B2 for high resistance or an open. See appropriate HEADLIGHT SYSTEMS & DAYTIME RUNNING LIGHTS wiring diagram. After repair, go to step  12 . If fault is not located and condition still exists, go to step  9 .
  8. Inspect for poor connections at ambient light sensor. After repair, go to step  12 . If fault is not located and condition still exists, go to step  10 .
  9. Inspect for poor connections at BCM harness connector C2. After repair, go to step  12 . If fault is not located and condition still exists, go to step  11 .
  10. Replace ambient light sensor. After repair, go to step  12 .
  11. Replace BCM. See BODY CONTROL MODULE (BCM)  under REMOVAL & INSTALLATION. After replacement, perform set up procedure. See NEW BCM SETUP  under PROGRAMMING. After replacement, go to next step.
  12. Using scan tool, clear BCM DTCs. Operate vehicle within conditions to set DTC. If DTC B2647 resets, return to step  2 . If DTC B2647 does not reset, system is okay.
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