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HOMESERVICE MANUALSCHEVROLET2008CHEVY EXPRESS G2500, VAN CARGO, 6.6 6REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 1306 (INSTRUMENT PANEL SYSTEM DISPLAYS & GAGES)DIAGNOSTIC INFORMATION AND PROCEDURESDTC P0608CIRCUIT/SYSTEM TESTING
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6

Circuit/System Testing

2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6SECTION Circuit/System Testing
WARNING: This page is about a different car, the 2008 Cadillac STS. However, it is still accessible from the selected car via links, so may be relevant.
IMPORTANT: The drive wheels of the vehicle must be raised and the transmission must be placed in drive or first gear. Refer to Lifting and Jacking the Vehicle .
  1. Ignition OFF, disconnect the harness connector at the rear object sensor control module.
  2. With the drive wheels raised start the engine and place the vehicle transmission in drive or the first gear. Verify that the speedometer value does not match the scan tool Vehicle Speed parameter in the ECM Engine Data List.
    • If the speedometer matches the scan tool Vehicle Speed parameter, test the vehicle speed signal circuit terminal 18 for a short to voltage, a short to ground or an open/high resistance. If the circuit tests normal, replace the rear object sensor control module.
  3. Ignition OFF, disconnect the harness connector at the inside rearview mirror (ISRVM).
  4. With the drive wheels raised start the engine and place the vehicle transmission in drive or the first gear. Verify that the speedometer value does not match the scan tool Vehicle Speed parameter in the ECM Engine Data List.
    • If the speedometer matches the scan tool Vehicle Speed parameter, test the vehicle speed signal circuit terminal 6 for a short to voltage, a short to ground or an open/high resistance. If circuit tests normal, replace the ISRVM.
  5. Ignition OFF disconnect the X1 (LH2 and LC3) or X2 (LY7) harness connector at the engine control module.
  6. Ignition ON, test for 9-11 volts between the vehicle speed signal circuit terminal 39 (LH2 and LC3) or terminal 22 (LY7) and ground.
    • If less than 9 volts, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the radio.
    • If greater than 11 volts, test the signal circuit for a short to voltage. If the circuit tests normal, replace the radio.
  7. If all circuits test normal, test or replace the ECM.
RENDER: 1.0x

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When to See a Mechanic

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

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