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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 141 (Engine Control System & Fuel - 4.8L, 5.3L, 6.0L And 6.2L - DTC P0010 To DTC P0333) >> DTC P0128 >> Circuit/System Testing

Circuit/System Testing

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IMPORTANT: All electrical components and accessories must be turned OFF and allowed to power down.
  1. Ignition OFF, disconnect the ECT harness connector at the ECT sensor.
  2. Ignition OFF, test for less than 5 ohms of resistance between the low reference circuit 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 ECT Sensor parameter is less than -39°C (-38°F).
    • If greater than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM.
  4. Install a 3A fused jumper wire between the signal circuit and the low reference circuit. Verify the scan tool ECT Sensor parameter is greater than 149°C (300°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.
  5. If all circuits test normal, test or replace the ECT sensor.
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