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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 P176B-P176D, P178F, or P17D3 >> 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.
    NOTE:

    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. Disconnect the electrical connector: X1 @ T12 Automatic Transmission Assembly
  3. Ignition - On/Vehicle - In Service Mode
  4. Test for 8.3 to 9.6 V between the test points: 9 V Reference circuit terminal 7 & Ground
    • If less than 8.3 V 
    1. Ignition/Vehicle - Off
    2. Disconnect the electrical connector: K71 Transmission Control Module
    3. Test for infinite resistance between the test points: 9 V Reference circuit terminal 7@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: 9 V Reference circuit terminal 7@Component harness & Terminal 7@ 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 greater than 9.6 V 
    1. Ignition/Vehicle - Off
    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: 9 V Reference circuit terminal 7 @ 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 between 8.3 and 9.6 V 
  5. Ignition/Vehicle - Off
  6. Install & Setup - EL-38522 Variable Signal Generator
    • Voltage - 5 V
    • Frequency - 5, 000 Hz
    • Duty Cycle - 10%
    • Black lead@Ground
    • Red lead@Signal circuit terminal 2
  7. Ignition - On/Vehicle - In Service Mode
  8. Verify the scan tool parameter: Transmission Intermediate Speed Sensor 1 = 3, 710 to 3, 780 RPM
    • If not between 3, 710 and 3, 780 RPM 
    1. Ignition/Vehicle - Off
    2. Disconnect the electrical connector: K71 Transmission Control Module
    3. Test for infinite resistance between the test points: Signal circuit terminal 2@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: Signal circuit terminal 2@Component harness & Terminal 13@ Control module harness
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
    5. Ignition - On/Vehicle - In Service Mode
    6. Test for less than 1 V between the test points: Signal circuit terminal 2@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 less than 1 V
    • Go to next step: If between 3, 710 and 3, 780 RPM 
  9. Verify the scan tool parameter: Transmission Intermediate Speed Sensor 1 Direction Signal = 0.02 ms
    • If not the specified value 

      Replace the component: K71 Transmission Control Module

    • Go to next step: If the specified value 
  10. EL-38522 Variable Signal Generator - 600 Hz
  11. Verify the scan tool parameter: Transmission Intermediate Speed Sensor 1 Direction Signal = 0.17
    • If not the specified value 

      Replace the component: K71 Transmission Control Module

    • Go to next step: If the specified value 
  12. Ignition/Vehicle - Off
  13. Connect the electrical connector: X1@T12 Automatic Transmission Assembly
  14. Remove the component: Automatic Transmission Fluid Pan
  15. Disconnect the electrical connector: B14DA Transmission Intermediate Speed Sensor 1
  16. Ignition - On/Vehicle - In Service Mode
  17. Test for 8.3 to 9.6 V between the test points: 9 V Reference circuit terminal 2 & Ground
    • If not between 8.3 and 9.6 V 

      Replace the component: Automatic Transmission Wiring Harness

    • Go to next step: If between 8.3 and 9.6 V 
  18. Ignition Off
  19. Install & Setup - EL-38522 Variable Signal Generator
    • Voltage - 5 V
    • Frequency - 5, 000 Hz
    • Duty Cycle - 10%
    • Black lead@Ground
    • Red lead@Signal circuit terminal 1
  20. Ignition - On/Vehicle - In Service Mode
  21. Verify the scan tool parameter: Transmission Intermediate Speed Sensor 1 = 3, 710 to 3, 780 RPM
    • If not between 3, 710 and 3, 780 RPM 

      Replace the component: Automatic Transmission Wiring Harness

    • Go to next step: If between 3, 710 and 3, 780 RPM 
  22. Test or replace the component: B14DA Transmission Intermediate Speed Sensor 1
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