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Home >> Chevrolet >> 2007 >> Chevy Express G2500, Van Cargo, 6.6 6 >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 10 (Engine Control System & Fuel System - 6.6L (LLY) - DTC P0016 To DTC P0341) >> DTC P0128 >> Circuit/System Testing

Circuit/System Testing

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  1. Verify the proper heat range and for a stuck open thermostat. Refer to Thermostat Diagnosis .
  2. Ignition OFF, disconnect the harness connector at the ECT sensor.
  3. Ignition OFF, test for less than 5 ohms of resistance between the low reference circuit terminal A 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 control module.
  4. Ignition ON, verify the scan tool ECT parameter is less than -39°C (-40°F).
    • If greater than the specified range, test the signal circuit terminal B for a short to ground. If the circuit tests normal, replace the control module.
  5. Install a 3A fused jumper wire between the signal circuit terminal B and the low reference circuit terminal A. Verify the scan tool ECT 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 control module.
  6. If all circuits test normal, test or replace the ECT sensor.
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