Circuit/System Testing

2006 Isuzu Ascender S, 5.3 M, 4WDSECTION Circuit/System Testing
WARNING: This page is about a different car, the 2008 Isuzu Ascender, 2008 GMC Envoy, and 2008 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the harness connector at an affected component.
  2. Test for less than 1 ohm of resistance between the affected component ground circuit terminal listed below and ground.
    • Transfer case shift control switch terminal D
    • IPC terminal A5
    • HVAC control module terminal B9 X1
    • Rear window wiper/washer switch terminal B
    • Headlamp switch terminal C X1
    • Upper right steering wheel switch terminal 5
    • Upper left steering wheel switch terminal 3
    • Lower left steering wheel switch terminal 4
    • Lower right steering wheel switch terminal 4
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Connect a test lamp between the listed control circuit terminal and ground circuit terminal.
    • Transfer case shift control switch terminal C to terminal D
    • IPC terminal A7 to terminal A5
    • HVAC control module terminal A7 X1 to terminal B9 X1
    • Rear window wiper/washer switch terminal C to terminal B
    • Headlamp switch terminal B X1 to terminal C X1
    • Upper right steering wheel switch terminal 3 to terminal 5
    • Upper left steering wheel switch terminal 2 to terminal 3
    • Lower left steering wheel switch terminal 1 to terminal 4
    • Lower right steering wheel switch terminal 1 to terminal 4
  4. Command the lamp dimming test ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    • If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
    • If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  5. If all circuits test normal, test or replace the affected component.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • β€’ You smell fuel, burning insulation, or see smoke.
  • β€’ Brakes feel soft, pull hard to one side, or make grinding noises.
  • β€’ The engine overheats, stalls repeatedly, or misfires under load.
  • β€’ You are missing required tools, torque specs, or safe lifting equipment.
  • β€’ You are not confident in the next step or safety outcome.