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Home >> Buick >> 2018 >> Envision Preferred, AWD >> Repair and Diagnosis >> Accessories & Equipment >> Gauges & Instrument Panels >> Instrument Panel System Displays And Gauges >> Diagnostic Information and Procedures >> DTC P0071-P0074 >> Circuit/System Testing

Circuit/System Testing

    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: B9 Ambient Air Temperature Sensor
  3. Test for less than 10 ohms between the test points: Low Reference circuit terminal B (or2) & Ground
    • If 10 ohms or greater 
    1. Disconnect the electrical connector: K20 Engine Control Module
    2. Test for less than 2 ohms between the test points: Low Reference circuit terminal B(or2)@Component harness & The other end of the circuit
      • 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: Ambient Air Temperature = Less than -34°C (-30°F)
    • If -34°C (-30°F) or warmer 
    1. Ignition/Vehicle - Off
    2. Disconnect the electrical connector: K20 Engine Control Module
    3. Test for infinite resistance between the test points: Signal circuit terminal A (or1)@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 -35°C (-31°F) or colder 
  6. Connect a 3 A fused jumper wire between the test points: Signal circuit terminal A (or1) & Low Reference circuit terminal B (or2)
  7. Verify the scan tool parameter: Ambient Air Temperature = Greater than 143°C (290°F)
    • If 143°C (290°F) or colder 
    1. Ignition/Vehicle - Off & Remove - Jumper wire(s)
    2. Disconnect the 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@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@Component harness & The other end of the circuit
      • 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 144°C (291°F) or warmer 
  8. Apply dielectric grease to connector terminals.
  9. Connect the component: B9 Ambient Air Temperature Sensor
  10. Operate the vehicle within the Conditions for Running the DTC.
  11. Verify the repair corrected the DTC/symptom.
    • If the repair did not correct the DTC/symptom 

      Test or replace the component: B9 Ambient Air Temperature Sensor

    • Go to next step: If the repair corrected the DTC/symptom 
  12. All OK.
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