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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1045 (Engine Controls And Fuel - 4.3L - DTC P0016 To DTC P0336) >> DTC P0128 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2008 GMC Sierra and 2008 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
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 pin A and ground.
    • If greater than the specified range, test the low reference circuit pin A 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 pin B for a short to ground. If the circuit tests normal, replace the ECM.
  4. Install a 3A fused jumper wire between the signal circuit pin B and the low reference circuit pin A. Verify the scan tool ECT Sensor parameter is greater than 149°C (300°F).
    • If less than the specified range, test the signal circuit pin B 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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