Circuit/System Testing

2008 Chevrolet Chevy Express G3500, Van Passenger ExtendedSECTION Circuit/System Testing
WARNING: This page is about a different car, the 2010 Cadillac STS. However, it is still accessible from the selected car via links, so may be relevant.

Interior Trunk Release Switch Malfunction

  1. Ignition OFF, disconnect the harness connector at the interior rear compartment lid release switch.
  2. Test for less than 10 ohms between the ground circuit terminal 1 and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool Trunk Release Switch parameter is Inactive.
    • If not the specified value, test the signal circuit terminal 3 for a short to ground. If the circuit tests normal, replace the driver window switch.
  4. Install a 3A fused jumper wire between the signal circuit terminal 3 and ground. Verify the scan tool Trunk Release Switch parameter is Active.
    • If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the driver window switch.
  5. If the circuits test normal, test or replace the interior rear compartment lid release switch.

Exterior Trunk Release Switch Malfunction

  1. Ignition OFF, disconnect the harness connector at the exterior rear compartment lid release switch.
  2. Test for less than 5 ohms between the ground circuit terminal C and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool Trunk Release Switch parameter is Inactive.
    • If not the specified value, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the RCDLR.
  4. Install a 3A fused jumper wire between the signal circuit terminal A and ground. Verify the scan tool scan tool Trunk Release Switch parameter is Active.
    • If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the RCDLR.
  5. If all circuits test normal, test or replace the exterior rear compartment lid release switch.

Valet Switch Malfunction

  1. Ignition OFF, disconnect the harness connector at the valet switch.
  2. Ignition ON, verify a test lamp illuminates between the B+ circuit terminal A and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  3. Verify the scan tool Valet Switch parameter is Inactive.
    • If not the specified value, test the signal circuit terminal B for a short to voltage. If the circuit tests normal, replace the IPM.
  4. Install a 3A fused jumper wire between the signal circuit terminal B and the B+ circuit terminal A. Verify the scan tool Valet Switch parameter is Active.
    • If not the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the IPM.
  5. If all circuits test normal, test or replace the valet switch.

Trunk Release Malfunction

  1. Ignition OFF, disconnect the TRUNK RELSE relay.
  2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal R33 and ground.
    • If the test lamp illuminates, test the control circuit for a short to voltage.
  3. Verify that a test lamp illuminates between the B+ circuit terminal R32 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the control circuit terminal R33 for a short to ground.
  4. Verify that a test lamp illuminates between the B+ circuit terminal R31 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  5. Ignition OFF, disconnect the harness connector at the rear compartment lid latch.
  6. Test for less than 5 ohms between the ground circuit terminal B and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  7. Connect the harness connector at the rear compartment lid latch.
  8. Ignition ON, connect a 40A fused jumper wire between the B+ circuit terminal R32 and the control circuit terminal R33. Verify the rear compartment lid release actuator is activated.
    • If the rear compartment lid release actuator does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the rear compartment lid latch.
  9. Connect a test lamp between the B+ circuit terminal R31 and the control circuit terminal R35.
  10. Command the Trunk Release Relay 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 ground. If the circuit tests normal, replace the RIM.
    • If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the RIM.
  11. If all circuits test normal, test or replace the TRUNK RELSE relay.
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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.