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Home >> Cadillac >> 2021 >> CT4 Sport, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 122 (Engine Controls And Fuel - 2.7L (L3B) - Diagnostic Information And Procedures (3 Of 3)) >> Diagnostic Information and Procedures >> DTC P2AB8, P2AB9, P2B81, P2B93, P2C9B, or U0644 >> Circuit/System Verification

Circuit/System Verification

WARNING: This page is about a different car, the 2022 Cadillac CT4. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition - On / Vehicle - In Service Mode
  2. Verify DTC DTC P0641, P0651, P0697, or P06A3 is not set.
    • Go to next step: If none of the DTCs are set 
  3. Verify DTC P2AB8, P2AB9 is not set.
    • If any of the DTCs are set 

      Replace the component: M128 Turbocharger Wastegate Actuator

    • Go to next step: If none of the DTCs are set 
  4. Verify DTC U0644 is not set.
    • If the DTC is set 

      Refer to: Circuit/System Testing - Test 1

    • Go to next step: If the DTC is not set 
  5. Engine - Idling - At normal operating temperature
  6. Perform the scan tool control function: Turbocharger Wastegate Position - Command the component to the maximum position/speed & Release Control

    Verify the scan tool parameter: Turbocharger Wastegate Position Sensor = Desired Turbocharger Wastegate Position

    • If not equal 

      Refer to: Circuit/System Testing - Test 2

    • Go to next step: If equal 
  7. Perform the scan tool control function: Turbocharger Wastegate Position - Command the component to the maximum position/speed

    Verify the scan tool parameter: Turbocharger Wastegate Position Sensor = The value should not spike or drop out.

    • Perform the action while monitoring the parameter:
    • Wiggle the harness and connector: M128 Turbocharger Wastegate Actuator
    • Wiggle the harness and connector: K20 Engine Control Module
    • If the value spikes or drops out 

      Repair as necessary - Wiring / Terminal (s) / Electrical Connector (s)

    • Go to next step: If the value does not spike or drop out 
  8. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

    Verify the DTC does not set.

    • If the DTC sets 

      Repeat the procedure starting at step 3

    • Go to next step: If the DTC does not set 
  9. All OK.
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