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Home >> Cadillac >> 2021 >> CT5 Sport, RWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 5 (Engine Controls And Fuel - 3.0L (LGY) - Diagnostic Information And Procedures (1 Of 2)) >> Diagnostic Information and Procedures >> DTC P0121-P0123, P0222, P0223, P2135, U0606, or U0607 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different variant/trim than selected.
    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. NOTE:

    Disconnecting the component electrical connector causes additional DTCs to set.

  2. Disconnect the electrical connector: Charge Air Cooler Cover
    3. NOTE:

    Testing for steps 4 to 9 is performed on the control module K20 side of the harness connector.

  3. Test for less than 5 Ω between the test points: Low Reference circuit terminal 4 & The other end of the circuit @ Chassis Ground
    • If 5 Ω or greater 
    1. Disconnect the appropriate electrical connector: K20 Engine Control Module
    2. Test for less than 2 Ω between the test points: Low Reference circuit terminal 4 @ Component harness & The other end of the circuit @ Control module harness
      • If 2 Ω or greater - Repair the open/high resistance in the circuit.
      • If less than 2 Ω - Replace the component: K20 Engine Control Module
    • Go to next step: If less than 5 Ω 
  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 5 & Low Reference circuit terminal 4
    • If less than 4.8 V 
    1. Ignition/Vehicle - Off
    2. Disconnect the appropriate electrical connector: K20 Engine Control Module
    3. Test for infinite resistance between the test points: 5 V Reference circuit terminal 5 @ Component harness & The other end of the circuit @ Chassis 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 Ω between the test points: 5 V Reference circuit terminal 5 @ Component harness & The other end of the circuit @ Control module harness
      • If 2 Ω or greater - Repair the open/high resistance in the circuit.
      • If less than 2 Ω - Replace the component: K20 Engine Control Module
    • If greater than 5.2 V 
    1. Ignition/Vehicle - Off
    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: 5 V Reference circuit terminal 5 @ Component harness & The other end of the circuit @ Chassis 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 4.8 to 5.2 V between the test points: Serial Data circuit terminal 3 & Ground
    • If less than 4.8 V 
    1. Ignition/Vehicle - Off
    2. Disconnect the appropriate electrical connector: K20 Engine Control Module
    3. Test for infinite resistance between the test points: Serial Data circuit terminal 3 @ Component harness & The other end of the circuit @ Chassis 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 Ω between the test points: Serial Data circuit terminal 3 The other end of the circuit
      • If 2 Ω or greater - Repair the open/high resistance in the circuit.
      • If less than 2 Ω - Replace the component: K20 Engine Control Module
    • If greater than 5.2 V 
    1. Ignition/Vehicle - Off
    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: Serial Data circuit terminal 3 @ Component harness & The other end of the circuit @ Chassis Ground
      • If 1 V or greater - Repair the short to voltage on the circuit.
      • Go to next step: If less than 1 V - Replace the component: K20 Engine Control Module
    • Go to next step: If between 4.8 and 5.2 V 
  7. Ignition/Vehicle - Off
  8. Remove - Charge Air Cooler Cover

    Refer to Charge Air Cooler Cover Replacement

  9. Connect the electrical connector: X25 Charge Air Cooler Cover Connector
  10. Disconnect the appropriate electrical connector: Q38 Throttle Body
  11. Test for less than 5 Ω between the test points: Low Reference circuit terminal 4 & Ground
    • If 5 Ω or greater 

      Test or replace the component: Jumper Harness @ Q38 Throttle Body

    • Go to next step: If less than 5 Ω 
  12. Ignition - On / Vehicle - In Service Mode
  13. Test for 4.8 to 5.2 V between the test points:
    • Serial Data circuit terminal 3 & Ground
    • 5 V Reference circuit terminal 2 & Ground
    • If not between 4.8 and 5.2 V 

      Test or replace the component: Jumper Harness @ Q38 Throttle Body

    • Go to next step: If between 4.8 and 5.2 V 
  14. Test or replace the component: Q38 Throttle Body
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