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HOMESERVICE MANUALSCHEVROLET2008CHEVY EXPRESS G2500, VAN CARGO, 6.6 6REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 1901 (ENGINE CONTROL SYSTEM & FUEL SYSTEM - 6.6L LMM - DTC P1224 TO DTC P2463)DTC P154CCIRCUIT/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 does not describe the selected car, but rather 6 other vehicles, including the 2009 GMC Savana Special, 2009 GMC Savana Camper Special, 2009 GMC Savana, 2009 Chevrolet RV Cutaway, and 2009 Chevrolet Cutaway. However, it is still accessible from the selected car via links, so may be relevant.
IMPORTANT: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
  1. Test the IAH current signal circuit between IAH terminal 4 X1 and GPCM terminal 29 X2 for an open, a short to ground, or a short to voltage:
  2. Ignition OFF, disconnect the X1 harness connector of the IAH. Connect any other circuits that were previously disconnected.
    3. IMPORTANT: Set the DMM to the 4V DC hertz scale.
  3. Turn ON the ignition. With a DMM measure between command 2 circuit terminal 3 of the connector and a good ground for 0.78-1.1 Hz.
    • If the DMM does not measure between 0.78-1.1 Hz, replace the GPCM.
    4. IMPORTANT:
    • Do not supply 12 volts to terminal 2 on the IAH for more than 20 seconds.
    • Set the DMM to the 4V DC hertz scale.
  4. Turn OFF the ignition. Install a jumper wire between temperature signal circuit terminal 1 of the connector and the corresponding terminal on the IAH.
  5. Install a jumper wire between the IAH harness command 2 circuit terminal 3 of the connector and the corresponding terminal on the IAH.
  6. Supply 12 volts to terminal 2 on the IAH.
  7. Turn ON the ignition. Measure for 1 hertz on terminal 4 at the IAH.
    • If 0.7-1.1 hertz is measured on terminal 4, replace the GPCM.
    • If 0.7-1.1 hertz is not measured on terminal 4, replace the IAH.
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.