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Home >> Chevrolet >> 2018 >> Spark LT, Automatic CVT Trans >> Repair and Diagnosis >> External Pages >> Different car >> Section 52 (Engine Controls And Fuel - 1.4L (LV7) - DTC P0010 To DTC P0366) >> Diagnostic Information and Procedures >> DTC P0128: Engine Coolant Temperature (ECT) Below Thermostat Regulating Temperature >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2017 Chevrolet Spark. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:

It may take up to 2 min for all vehicle systems to power down before an accurate ground or low reference circuit continuity test can be performed.

  1. Ignition/Vehicle & All vehicle systems - Off
  2. Disconnect the electrical connector: B34 Engine Coolant Temperature Sensor
  3. Test for less than 10 ohms between the test points: Low Reference circuit terminal 2 & Ground
    • If 10 ohms or greater 
    1. Disconnect the electrical connector: X2 @ K20 Engine Control Module
    2. Test for less than 2 ohms between the test points: Low Reference circuit terminal 2 @ Component harness & Terminal 43 @ Control module harness
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Test or replace the component: K20 Engine Control Module
    • If less than 10 ohms 
  4. Ignition - On/Vehicle - In Service Mode
  5. Verify the scan tool parameter: ECT Sensor = Colder than -39°C (-38°F)
    • If -39°C (-38°F) or warmer 
    1. Ignition/Vehicle - Off
    2. Disconnect the electrical connector: X2 @ K20 Engine Control Module
    3. Test for infinite resistance between the test points: Signal circuit terminal 1 @ Component harness & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • If infinite resistance - Replace the component: K20 Engine Control Module
    • If colder than -39°C (-38°F) 
    6. CAUTION:

    If the fuse in the jumper wire opens, the signal circuit may have a short to a voltage or a short to ground and the sensor might be damaged.

  6. Connect a 3 A fused jumper wire between the test points: Signal circuit terminal 1 & Low Reference circuit terminal 2
  7. Verify the scan tool parameter: ECT Sensor = Warmer than +139°C (+282°F)
    • If +139°C (+282°F) or colder 
    1. Ignition/Vehicle - Off & Remove - Jumper wire(s)
    2. Disconnect the electrical connector: X2 @ K20 Engine Control Module
    3. Ignition - On/Vehicle - In Service Mode
    4. Test for less than 1 V between the test points: Signal circuit terminal 1 @ Component harness & Ground
      • If 1 V or greater - Repair the short to voltage on the circuit.
      • If less than 1 V
    5. Ignition/Vehicle - Off
    6. Test for less than 2 ohms between the test points: Signal circuit terminal 1 @ Component harness & Terminal 2 @ Control module harness
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Replace the component: K20 Engine Control Module
    • If warmer than +139°C (+282°F) 
  8. Replace the component: B34 Engine Coolant Temperature Sensor
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