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Home >> GMC >> 2018 >> Acadia Denali, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 89 (Engine Controls And Fuel - 3.6L (LF4 LGX) - DTC P0121 LF4 To DTC P0685 LF4) >> Diagnostic Information and Procedures >> DTC P0128: Engine Coolant Temperature (ECT) Below Thermostat Regulating Temperature (LF4) >> Component Testing

Component Testing

WARNING: This page is about a different car, the 2016 Cadillac ATS. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the harness connector at the B34 Engine Coolant Temperature Sensor.
  2. Test the ECT sensor by varying the sensor temperature while monitoring the sensor resistance.
  3. Verify the readings are within the range specified in the Temperature Versus Resistance - Engine Coolant Temperature Sensor table.
    • If not within the specified range 

      Replace the B34 Engine Coolant Temperature Sensor.

    • If within the specified range 
  4. Test for infinite resistance between each terminal and the sensor housing.
    • If less than infinite resistance 

      Replace the B34 Engine Coolant Temperature Sensor.

    • If infinite resistance 
  5. Refer to Thermostat Diagnosis .
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