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Home >> Cadillac >> 2021 >> XT5 Sport >> Repair and Diagnosis >> External Pages >> Different car >> Section 838 (Automatic Transmission - 10L1000 (MGM MGU) - Diagnostic Information And Procedures (1 Of 2)) >> Diagnostic Information and Procedures >> DTC P0964, P0966, or P0967 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2023 GMC Sierra 3500 HD and 2023 GMC Sierra 2500 HD. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition/Vehicle - Off
  2. Disconnect the electrical connector: X1@T12 Automatic Transmission Assembly
  3. Connect a test lamp between the test points: Control circuit terminal 9@Component harness & Ground
  4. Ignition - On/Vehicle - In Service Mode
    5. NOTE:

    If unable to perform the scan tool control function due to Device Limits Exceeded and/or DTC Present, jumper the component B14A circuits between the component T12 connector and the X1 harness connector.

    • Connect a 3 A fused jumper wire between the test points: 9 V Reference circuit terminal 7 X1 (harness side) & 9 V Reference circuit terminal 7 X1 (component side)
    • Connect a 3 A fused jumper wire between the test points: Signal circuit terminal 4 X1 (harness side) & Signal circuit terminal 4 X1 (component side)
  5. Perform the scan tool control function: High Side Driver 2 - On and Off

    Verify the test lamp turns On and Off.

    • If the test lamp is always Off 
    1. Ignition/Vehicle - Off & Remove - Test lamp
    2. Disconnect the electrical connector: K71 Transmission Control Module
    3. Test for infinite resistance between the test points: Control circuit terminal 9@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: Control circuit terminal 9@Component harness & Control circuit terminal 49@ Control module harness
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Replace the component: K71 Transmission Control Module
    • If the test lamp is always On 
    1. Ignition/Vehicle - Off & Remove - Test lamp
    2. Disconnect the electrical connector: K71 Transmission Control Module
    3. Ignition - On/Vehicle - In Service Mode
    4. Test for less than 1 V between the test points: Control circuit terminal 9@Component harness & Ground
      • If 1 V or greater - Repair the short to voltage on the circuit.
      • If less than 1 V - Replace the component: K71 Transmission Control Module
    • Go to next step: If the test lamp turns On and Off 
  6. Connect a test lamp between the test points: Control circuit terminal 9@Component harness & Control circuit terminal 15@Component harness
  7. Perform the scan tool control function: Transmission Control Solenoid Valve 2 - On and Off

    Verify the test lamp turns On and Off.

    • If the test lamp is always Off 
    1. Ignition/Vehicle - Off & Remove - Test lamp
    2. Disconnect the electrical connector: K71 Transmission Control Module
    3. Test for less than 2 ohms between the test points: Control circuit terminal 15@Component harness & Control circuit terminal 2@ Control module harness
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • Go to next step: If less than 2 ohms
    4. Ignition - On/Vehicle - In Service Mode
    5. Test for less than 1 V between the test points: Control circuit terminal 15@Component harness & Ground
      • If 1 V or greater - Repair the short to voltage on the circuit.
      • If less than 1 V - Replace the component: K71 Transmission Control Module
    • If the test lamp is always On 
    1. Ignition/Vehicle - Off & Remove - Test lamp
    2. Disconnect the electrical connector: K71 Transmission Control Module
    3. Test for infinite resistance between the test points: Control circuit terminal 15@Component harness & Ground
    • If less than infinite resistance - Repair the short to ground on the circuit.
    • If infinite resistance - Replace the component: K71 Transmission Control Module
    • Go to next step: If the test lamp turns On and Off 
  8. Ignition/Vehicle - Off & Remove - Test lamp
  9. Connect the electrical connector: X1@T12 Automatic Transmission Assembly
  10. Remove the component: Transmission Fluid Pan
  11. Disconnect the electrical connector: X177
  12. Connect a test lamp between the test points: Control circuit terminal 18@Component harness & Control circuit terminal 16@Component harness
  13. Perform the scan tool control function: Transmission Control Solenoid Valve 2 - On and Off

    Verify the test lamp turns On and Off.

    • If the test lamp does not turn On and Off 

      Replace the component: Automatic Transmission Wiring Harness - Pass-Thru

    • Go to next step: If the test lamp turns On and Off 
  14. Ignition/Vehicle - Off & Remove - Test lamp
  15. Connect the electrical connector: X177
  16. Disconnect the electrical connector: Q77B Transmission Control Solenoid Valve 2
  17. Connect a test lamp between the test points: Control circuit terminal 1 & Control circuit terminal 2@Component harness
  18. Perform the scan tool control function: Transmission Control Solenoid Valve 2 - On and Off

    Verify the test lamp turns On and Off.

    • If the test lamp does not turn On and Off 

      Replace the component: Automatic Transmission Wiring Harness - Main/Solenoid

    • Go to next step: If the test lamp turns On and Off 
  19. Test or replace the component: Q77B Transmission Control Solenoid Valve 2
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