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 2009 Cadillac STS. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the MAF/IAT harness connector at the MAF/IAT sensor.
  2. Ignition OFF for 90 seconds, test for less than 5 ohms of resistance between the low reference circuit terminal D and ground.
    • If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  3. Ignition ON, verify the scan tool IAT Sensor parameter is less than -39Β°C (-38Β°F).
    • If greater than the specified range, test the signal circuit terminal E for a short to ground. If the circuit tests normal, replace the ECM.
  4. IMPORTANT: If the 3A fuse in the jumper wire opens, the signal circuit is shorted to a voltage and the sensor may be damaged.
  5. Install a 3A fused jumper wire between the signal circuit terminal E and a ground. Verify the scan tool IAT Sensor parameter is greater than 149Β°C (300Β°F).
    • If less than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
  6. If all circuits test normal, test or replace the MAF/IAT sensor.
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When to See a Mechanic

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

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