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Circuit/System Testing

WARNING: This page is about a different car, the 2009 GMC Sierra, 2009 GMC Cab & Chassis Sierra, 2009 Chevrolet Silverado, and 2009 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 between terminal 27 X2 of the GPCM and terminal 6 X1 of the IAH for an open, a short to ground, or a short to voltage.
    • If a condition is found, repair as necessary.
  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 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 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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