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Home >> Isuzu >> 2007 >> i-290 LS, Standard >> Repair and Diagnosis >> External Pages >> Different car >> Section 39 (Lighting Systems) >> Diagnostic Information and Procedures >> Interior Backlighting Malfunction >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2007 Cadillac DTS. However, it is still accessible from the selected car via links, so may be relevant.

Dimmer Switch Circuit Test

  1. Ignition OFF, disconnect the harness connector at the headlamp switch.
  2. Ignition OFF, verify that a test lamp illuminates between the ground circuit terminal 8 and B+.
    • If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool Dimming Control Signal parameter is less than 0.1 volts.
    • If greater than the specified range, test the signal circuit terminal 13 for a short to voltage. If the circuit tests normal, replace the BCM.
  4. Ignition ON, test for B+ between the I/P dimming voltage reference circuit terminal 15 and ground.
    • If less than the specified value, test the voltage reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  5. Install a 3A fused jumper wire between the signal circuit terminal 13 and the voltage reference circuit terminal 15. Verify the scan tool BCM Dimming Control Signal parameter is greater than 2.6 volts.
    • If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  6. If all circuits test normal, test or replace the headlamp switch.

Interior Backlighting Circuit Test

  1. Ignition OFF, disconnect the harness connector at the component with the inoperative backlighting.
  2. Test for less than 5.0 ohms of resistance between the appropriate ground circuit terminal listed below and ground.
    • Headlamp Switch terminal 8
    • Hazard Switch terminal B
    • Ashtray Lamp terminal B
    • HVAC Control Module terminal 11 C1
    • Driver Information Display Switch terminal 6
    • Clock terminal 2
    • Radio terminal 8 C1
    • Left Middle Door Window Switch terminal 1 -- Limo
    • Right Middle Door Window Switch terminal 1 -- Limo
    • Traction Control Switch terminal A
    • Floor Shifter Assembly terminal D C2
    • Garage Door Opener Transmitter terminal 3
    • Sunshade Switch terminal A
    • Sunroof Switch terminal 5
    • Left Rear Door Window Switch terminal 1
    • Left Rear Heated Seat Switch terminal J
    • Left Rear Seat Lumbar Switch terminal E
    • Right Rear Door Window Switch terminal 1
    • Right Rear Heated Seat Switch terminal J
    • Right Rear Seat Lumbar Switch terminal E
    • Auxiliary HVAC Control Module terminal 8
    • Right Steering Wheel Control Switch terminal 1
    • Left Steering Wheel Control Switch terminal 8
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Connect a test lamp between the appropriate supply voltage circuit terminal listed below and ground.

Incandescent Dimming

LED Dimming

Front Door Switch Backlighting Circuit Test

  1. Ignition OFF, disconnect the (C4) harness connector at the appropriate driver or front passenger door control module.
  2. Connect a 3A fused jumper wire between the low reference circuit terminal 4 and ground.
  3. Connect a test lamp between the indicator supply voltage circuit terminal 13 and B+. The heated and cooled seat switch backlighting should illuminate.
    • If the switch backlighting does not illuminate, replace the heated and cooled seat switch.
  4. If the switch backlighting tests normal, replace the door control module.
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