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HOMESERVICE MANUALSCHEVROLET2008CHEVY EXPRESS G3500, VAN PASSENGER EXTENDEDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT VARIANT/TRIMSECTION 14 (ENGINE CONTROL SYSTEM & FUEL SYSTEM - 6.6L (LMM) - DTC P0700 TO DTC P2463)DTC P154BCIRCUIT/SYSTEM TESTING
2008 Chevrolet Chevy Express G3500, Van Passenger Extended

Circuit/System Testing

2008 Chevrolet Chevy Express G3500, Van Passenger ExtendedSECTION Circuit/System Testing
WARNING: This page is about a different variant/trim than selected.
IMPORTANT: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
  1. Test the following circuits for an open, a short to ground, or a short to voltage:
    • The IAH command 1 circuit
    • The IAH command 2 circuit
    • The IAH voltage signal circuit
    • If a condition was found on any of the circuits repair as necessary.
  2. Connect any circuits that were disconnected. With the ignition ON and the engine OFF, observe that the scan tool displays the IA Heater Driver Shorted parameter as OK.
    • If the IA Heater Driver Shorted parameter displays Fault, replace the intake air heater.
  3. With the ignition ON and the engine OFF, observe that the scan tool displays the Glow Plug Driver Shorted parameter as OK.
    • If the Glow Plug Driver Shorted parameter displays Fault, replace the Glow Plug Control Module.
    4. IMPORTANT: Set the DMM to the 4V DC hertz scale.
  4. Disconnect the IAH. Turn ON the ignition. With a DMM measure between command 2 circuit terminal 3 and a good ground on the harness side of the connector for 0.78-1.1 Hz.
    • If the DMM does not measure between 0.78-1.1 Hz ohms, replace the GPCM.
    5. IMPORTANT:
    • Do not install the jumper wire between 12 volts and the command circuit for more the 20 seconds.
    • Set the DMM to the 4V AC hertz scale.
  5. Turn OFF the ignition. Install a jumper wire between the IAH harness temperature signal circuit terminal 1 and the corresponding terminal on the IAH.
  6. Install a jumper wire between the IAH harness command two circuit terminal 3 and the corresponding terminal on the IAH.
  7. Supply 12 volts to terminal 2 on the IAH.
  8. Turn ON the ignition. Measure for 1 hertz on terminal 5 at the IAH.
    • If 0.7-1.1 hertz is measured on terminal 5, replace the GPCM.
    • If 0.7-1.1 hertz is not measured on terminal 5, 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.