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Home >> GMC >> 2020 >> Terrain Denali, FWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 6 (Engine Controls And Fuel - 1.5L (LYX) - Diagnostic Information And Procedures (1 Of 2)) >> Diagnostic Information and Procedures >> DTC P0128 or P01F0 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different variant/trim than selected.
    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 1 & Ground
    • If 10 ohms or greater 
    1. Disconnect the appropriate electrical connector : X2 @ K20 Engine Control Module
    2. Test for less than 2 ohms between the test points : Low Reference circuit terminal 1 @ Component harness & Terminal 2 X2 @ 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
    • Go to next step : 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 appropriate electrical connector : X2 @ K20 Engine Control Module
    3. Test for infinite resistance between the test points : Signal circuit terminal 2 @ 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
    • Go to next step : If colder than -39°C (-38°F) 
  6. Connect a 3 A fused jumper wire between the test points : Signal circuit terminal 2 & Low Reference circuit terminal 1
  7. Verify the scan tool parameter : ECT Sensor = Warmer than 149°C (300°F)
    • If 149°C (300°F) or colder 
    1. Ignition/Vehicle - Off & Remove - Jumper wire(s)
    2. Disconnect the appropriate electrical connector : 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 2 @ Component harness & Ground
      • If 1 V or greater - Repair the short to voltage on the circuit.
      • Go to next step : If less than 1 V
    5. Ignition/Vehicle - Off
    6. Test for less than 2 ohms between the test points : Signal circuit terminal 2 @ Component harness & Terminal 43 X2 @ 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
    • Go to next step : If warmer than 149°C (300°F) 
  8. Test or replace the component : B34 Engine Coolant Temperature Sensor
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