LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Buick >> 2021 >> Envision Preferred, AWD >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Controls And Fuel - 2.0L (LSY) - Diagnostic Information And Procedures (2 Of 2) >> Diagnostic Information and Procedures >> DTC P2AB8, P2AB9, P2B81, P2B93, P2C9B, or U0644 >> Circuit/System Testing
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Circuit/System Testing

    NOTE:
    • Disconnecting the component electrical connector causes additional DTCs to set.
    • 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: M128 Turbocharger Wastegate Actuator
  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 electrical connector: X2 @ K20 Engine Control Module
    2. Test for less than 2 ohms between the test points: Low Reference circuit terminal 1 @ M128 Turbocharger Wastegate Actuator & The other end of the circuit @ 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. Test for 4.8 to 5.2 V between the test points: 5 V Reference circuit terminal 3 & Low Reference circuit terminal 1
    • If less than 4.8 V 
    1. Ignition/Vehicle - Off
    2. Disconnect the electrical connector: X2K20 Engine Control Module
    3. Test for infinite resistance between the test points: 5 V Reference circuit terminal 3 @ Component harness & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • Go to next step: If infinite resistance
    4. Test for less than 2 ohms between the test points: 5 V Reference circuit terminal 3 @ Component harness & The other end of the circuit @ 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 greater than 5.2 V 
    1. Ignition/Vehicle - Off
    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: 5 V Reference circuit terminal 3 @ Component harness & Ground
      • If 1 V or greater - Repair the short to voltage on the circuit.
      • If less than 1 V - Replace the component: K20 Engine Control Module
    • Go to next step: If between 4.8 and 5.2 V 
  6. Test for 3.75 to 4.25 V between the test points: Serial Data circuit terminal 2 @ Component harness & Ground
    • If less than 3.75 V 
    1. Ignition/Vehicle - Off
    2. Disconnect the electrical connector: X2K20 Engine Control Module
    3. Test for infinite resistance between the test points: Serial Data circuit terminal 2 @ Component harness & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • Go to next step: If infinite resistance
    4. Test for less than 2 ohms between the test points: Serial Data circuit terminal 2 @ Component harness & The other end of the circuit @ 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 greater than 4.25 V 
    1. Ignition/Vehicle - Off
    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: Serial Data circuit terminal 2 @ Component harness & Ground
      • If 1 V or greater - Repair the short to voltage on the circuit.
      • If less than 1 V - Replace the component: K20 Engine Control Module
    • Go to next step: If between 3.75 and 4.25 V 
  7. Test or replace the component: M128 Turbocharger Wastegate Actuator
scientia non olet · About LEMON Manuals