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Home >> Cadillac >> 2021 >> CT4 Sport, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 404 (Engine Controls And Fuel - 6.2L (LT4) - Diagnostic Information And Procedures (3 Of 3)) >> Diagnostic Information And Procedures >> DTC P3400, P3401, P3403, P3404, P3425, P3427, P3428, P3441, P3443, P3444, P3449, P3451, or P3452 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2022 Cadillac CT5. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition/Vehicle & All vehicle systems - Off
    2. NOTE:
    • The component is not accessible without disassembling the engine, so testing will begin at an inline harness connector.
    • Use the schematic to determine which inline harness connector must be disconnected for the following component: Q43 Valve Lifter Oil Manifold Assembly
  2. Disconnect the appropriate electrical connector: Inline Harness Connector
  3. Ignition - On/Vehicle - In Service Mode
    4. NOTE:

    Testing for steps 4 to 12 is performed on the control module K20 side of the harness connector.

  4. Verify a test lamp turns On between the test points: Ignition circuit terminal & Ground
    • If the test lamp does not turn On and the circuit fuse is OK 
    1. Ignition/Vehicle - Off & Remove - Test lamp
    2. Test for less than 2 ohms between the test points: Ignition circuit terminal@Inline Harness Connector & Output terminal@Fuse
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Verify the fuse is OK and there is voltage at the fuse.
    • If the test lamp does not turn On and the circuit fuse is open 
    1. Ignition/Vehicle - Off & Remove - Test lamp
      2. NOTE:

      The ignition circuit supplies voltage to other components. Test all circuits for a short to ground or test all components for being shorted.

    2. Test for infinite resistance between the test points: Ignition circuit terminal@Inline Harness Connector & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • If infinite resistance - Refer to step 13
    • Go to next step: If the test lamp turns On 
  5. Verify a test lamp does not turn On between the test points:
    • Control circuit terminal 1@Inline Harness Connector & B+
    • Control circuit terminal 2@Inline Harness Connector & B+
    • Control circuit terminal 3@Inline Harness Connector & B+
    • Control circuit terminal 5@Inline Harness Connector & B+
    • If the test lamp turns On 
    1. Ignition/Vehicle - Off & Remove - Test lamp
    2. Disconnect the appropriate electrical connector: K20 Engine Control Module
    3. Test for infinite resistance between the test points:
      • Control circuit terminal 1@Inline Harness Connector & Ground
      • Control circuit terminal 2@Inline Harness Connector & Ground
      • Control circuit terminal 3@Inline Harness Connector & Ground
      • Control circuit terminal 5@Inline Harness Connector & 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 the test lamp does not turn On 
  6. Remove - Test Lamp
  7. Perform the appropriate scan tool control function: Cylinder Deactivation Control Valve - Off

    Verify the scan tool parameter: Cylinder 1, 4, 6, 7 Deactivation Control Valve Control Circuit High Test Status = Not RunorOkay

    • If not the specified state 
    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:
      • Control circuit terminal 1@Inline Harness Connector & Ground
      • Control circuit terminal 2@Inline Harness Connector & Ground
      • Control circuit terminal 3@Inline Harness Connector & Ground
      • Control circuit terminal 5@Inline Harness Connector & 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 the specified state 
  8. Ignition/Vehicle - Off
  9. Connect a 3 A fused jumper wire between the test points:
    • {P3425, P3427} Control circuit terminal 1@Inline Harness Connector & Ignition circuit terminal@Inline Harness Connector
    • {P3441, P3443} Control circuit terminal 2@Inline Harness Connector & Ignition circuit terminal@Inline Harness Connector
    • {P3401, P3403} Control circuit terminal 3@Inline Harness Connector & Ignition circuit terminal@Inline Harness Connector
    • {P3449, P3451} Control circuit terminal 5@Inline Harness Connector & Ignition circuit terminal@Inline Harness Connector
  10. Ignition - On/Vehicle - In Service Mode
  11. Perform the appropriate scan tool control function: Cylinder Deactivation Control Valve - Off

    Verify the scan tool parameter: Cylinder 1, 4, 6, 7 Deactivation Control Valve Control Circuit High Test Status = Malfunction

    • If not the specified state 
    1. Ignition/Vehicle - Off & Remove - Jumper wire(s)
    2. Disconnect the appropriate electrical connector: K20 Engine Control Module
    3. Test for less than 2 ohms between the test points:
      • {P3425, P3427} Control circuit terminal 1@Inline Harness Connector & The other end of the circuit@Control module harness
      • {P3441, P3443} Control circuit terminal 2@Inline Harness Connector & The other end of the circuit@Control module harness
      • {P3401, P3403} Control circuit terminal 3@Inline Harness Connector & The other end of the circuit@Control module harness
      • {P3449, P3451} Control circuit terminal 5@Inline Harness Connector & 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 the specified state 
  12. Ignition/Vehicle & All vehicle systems - Off
    13. NOTE:

    Testing for steps 14 to 16 is performed on the component side of the harness connector.

  13. Test for 10 to 20 ohms between the test points:
    • Control circuit terminal 1@Inline Harness Connector & Ignition circuit terminal@Inline Harness Connector
    • Control circuit terminal 2@Inline Harness Connector & Ignition circuit terminal@Inline Harness Connector
    • Control circuit terminal 3@Inline Harness Connector & Ignition circuit terminal@Inline Harness Connector
    • Control circuit terminal 5@Inline Harness Connector & Ignition circuit terminal@Inline Harness Connector
    • If not between 10 and 20 ohms 
    1. Perform the following procedure/test: Component Testing - Static Test

      Verify the procedure/test passes.

      • If the procedure/test does not pass - Replace the component: Q43 Valve Lifter Oil Manifold
      • Go to next step: If the procedure/test passes
    2. Repair the open/high resistance in the circuit: Control CircuitorIgnition circuit
    • Go to next step: If between 10 and 20 ohms 
  14. Test for infinite resistance between the test points:
    • Ignition circuit terminal@Inline Harness Connector & Ground
    • Ignition circuit terminal@Inline Harness Connector & Each terminal of the harness connector
    • Ground & Each terminal of the harness connector
    • If less than infinite resistance 

      Repair short to ground on the circuit.

    • Go to next step: If infinite resistance 
  15. Perform the following procedure/test: Cylinder Deactivation (Active Fuel Management) Valve Lifter Oil Manifold Diagnosis and Testing

    Verify the procedure/test passes.

    • If the procedure/test does not pass 

      Replace the component: Q43 Valve Lifter Oil Manifold

    • Go to next step: If the procedure/test passes 
  16. All OK.
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