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Home >> Cadillac >> 2018 >> Escalade Base, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 21 (Automatic Transmission - 8L90 (M5U) - Diagnostic Information And Procedures) >> Diagnostic Information And Procedures >> DTC P2718, P2720, P2721, P2727, P2729, P2730, P281D, Or P281E: Transmission Control Solenoid Valve 4/5/8 Control Circuit(s) >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2018 Chevrolet Suburban 3500 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: X175 @ T12 Automatic Transmission Assembly
  3. Connect a test lamp between the test points: High Side Driver 1 - Control circuit terminal 18 & Ground
  4. Ignition - On/Vehicle - In Service Mode
  5. Perform the scan tool control function: High Side Driver 1 - On and Off

    Verify the test lamp turns On and Off.

    • Go to next step: If the test lamp turns On and Off 
  6. Remove - Test Lamp
  7. Ignition/Vehicle - Off
  8. Disconnect the electrical connector: K71 Transmission Control Module
  9. Ignition - On/Vehicle - In Service Mode
  10. Test for less than 1 V between the test points:
    • {P2718, P2720, P2721} Control circuit terminal 13 & Ground
    • {P2727, P2729, P2730} Control circuit terminal 14 & Ground
    • {P281B, P281D, P281E} Control circuit terminal 1 & Ground
    • If 1 V or greater 

      Repair the short to voltage on the circuit.

    • Go to next step: If less than 1 V 
  11. Ignition/Vehicle - Off
  12. Test for infinite resistance between the test points:
    • {P2718, P2720, P2721} Control circuit terminal 13 & Ground
    • {P2727, P2729, P2730} Control circuit terminal 14 & Ground
    • {P281B, P281D, P281E} Control circuit terminal 1 & Ground
    • If less than infinite resistance 

      Repair the short to ground on the circuit.

    • Go to next step: If infinite resistance 
  13. Test for less than 2 ohms between the test points:
    • {P2718, P2720, P2721} Control circuit terminal 13 & The other end of the circuit
    • {P2727, P2729, P2730} Control circuit terminal 14 & The other end of the circuit
    • {P281B, P281D, P281E} Control circuit terminal 1 & The other end of the circuit
    • If greater than 2 ohms 

      Repair the open/high resistance in the circuit.

    • Go to next step: If less than 2 ohms 
  14. Remove the component: Automatic Transmission Fluid Pan
  15. Connect the electrical connector: X175 @ T12 Automatic Transmission Assembly
  16. Disconnect the appropriate electrical connector:
    • {P2718, P2720, P2721} Q77D Transmission Control Solenoid Valve 4
    • {P2727, P2729, P2730} Q77E Transmission Control Solenoid Valve 5
    • {P281B, P281D, P281E} Q77H Transmission Control Solenoid Valve 8
  17. Ignition - On/Vehicle - In Service Mode
  18. Test for less than 1 V between the test points:
    • {P2718, P2720, P2721} Control circuit terminal 17 @ Control module harness & Ground
    • {P2727, P2729, P2730} Control circuit terminal 1 @ Control module harness & Ground
    • {P281B, P281D, P281E} Control circuit terminal 21 @ Control module harness & Ground
    • If 1 V or greater 

      Replace the component: Automatic Transmission Wiring Harness

    • Go to next step: If less than 1 V 
  19. Ignition/Vehicle - Off
  20. Test for infinite resistance between the test points:
    • {P2718, P2720, P2721} Control circuit terminal 17 @ Control module harness & Ground
    • {P2727, P2729, P2730} Control circuit terminal 1 @ Control module harness & Ground
    • {P281B, P281D, P281E} Control circuit terminal 21 @ Control module harness & Ground
    • If less than infinite resistance 

      Replace the component: Automatic Transmission Wiring Harness

    • Go to next step: If infinite resistance 
  21. Test for less than 2 ohms between the test points:
    • {P2718, P2720, P2721} Control circuit terminal 17 @ Control module harness & The other end of the circuit
    • {P2727, P2729, P2730} Control circuit terminal 1 @ Control module harness & The other end of the circuit
    • {P281B, P281D, P281E} Control circuit terminal 21 @ Control module harness & The other end of the circuit
    • If greater than 2 ohms 

      Replace the component: Automatic Transmission Wiring Harness

    • Go to next step: If less than 2 ohms 
  22. Test or replace the component: Q77 Transmission Control Solenoid Valve
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