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Circuit/System Testing

WARNING: This page is about a different car, the 2008 GMC Sierra, 2008 GMC Cab & Chassis Sierra, 2008 Chevrolet Silverado, and 2008 Chevrolet Cab & Chassis Silverado. 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 feedback signal circuit for an open, a short to ground, or a short to voltage.
    • If a condition is found, repair as necessary.
    2. IMPORTANT: Set the DMM to the 4V DC hertz scale.
  2. Turn ON the ignition with a DMM measure between command two 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.
    3. 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 DC hertz scale.
  3. Turn OFF the ignition. Install a jumper wire between the IAH harness temperature signal circuit terminal 1 and the corresponding terminal on the IAH.
  4. Install a jumper wire between the IAH harness command two circuit terminal 3 and the corresponding terminal on the IAH.
  5. Supply 12 volts to terminal 2 on the IAH.
  6. Turn ON the ignition. Measure for 1 hertz on terminal 6 at the IAH.
    • If 0.7-1.1 hertz is measured on terminal 6, replace the GPCM.
    • If 0.7-1.1 hertz is not measured on terminal 6, replace the IAH.
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