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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 P0658 or P0659 >> Component Testing

Component 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. Remove the component: Automatic Transmission Fluid Pan
  3. Disconnect the electrical connector:
    • Q77G Transmission Control Solenoid Valve 7
    • Q77H Transmission Control Solenoid Valve 8
    4. NOTE:

    The component's temperature should be 19 to 21°C (66 to 70°F) while testing.

  4. Test for the resistance listed below between the test points: Control terminal 1 & Control terminal 2
    • Q77G Transmission Control Solenoid Valve 7 = 4.5 to 5.5 ohms
    • Q77H Transmission Control Solenoid Valve 8 = 11.0 to 13.0 ohms
    • If the resistance is not within range 

      Replace the component that failed the test:

    • Q77G Transmission Control Solenoid Valve 7
    • Q77H Transmission Control Solenoid Valve 8
    • Go to next step: If the resistance is within range 
  5. Test for infinite resistance between the test points: Each terminal of the component & The component's housing
    • If less than infinite resistance 

      Replace the component: Q77 Transmission Control Solenoid Valve

    • Go to next step: If infinite resistance 
  6. All OK.
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