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Home >> Chevrolet >> 2024 >> Tahoe Commercial, 4WD >> Repair and Diagnosis >> Transmission >> Automatic Trans >> Automatic Transmission - 10L80 (MHS MHU MQC) - Diagnostic Information And Procedures (1 Of 2) >> Diagnostic Information and Procedures >> DTC P176B-P176D, P178F, or P17D3 >> Circuit/System Testing

Circuit/System Testing

  1. Ignition/Vehicle & All vehicle systems - Off
    2. NOTE:

    When the following connector is disconnected, the ignition cannot be turned off due to lack of a valid park input to the TCM. If the ignition needs to be turned off, the connector will need to be reconnected.

  2. Disconnect the electrical connector: X1 @ T12 Automatic Transmission
  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 - EL-38522 Variable Signal Generator
    • Voltage - 5 V
    • Frequency - 5 kHz
    • Duty Cycle - 10%
    • Black lead @ Battery Negative Post
    • Red lead @ Signal circuit terminal 2
  7. Ignition - On/Vehicle - In Service Mode
  8. Verify the scan tool parameter: Intermediate Speed Sensor = 5, 890 to 6, 090 RPM
    • If not between 5, 890 and 6, 090 RPM 
    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: Signal circuit terminal 2 @ Component harness & Ground
      • If 1 V or greater - Repair the short to voltage on the circuit.
      • Go to next step: If less than 1 V
    5. Ignition/Vehicle - Off
    6. 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
    7. 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.
      • If less than 2 ohms - Replace the component: K71 Transmission Control Module
    • Go to next step: If between 5, 890 and 6, 090 RPM 
  9. Verify the scan tool parameter: Intermediate Speed Sensor Direction = Forward
    • If not the specified state 

      Replace the component: K71 Transmission Control Module

    • Go to next step: If the specified state 
  10. Setup - EL-38522 Variable Signal Generator
    • Voltage - 5 V
    • Frequency - 600 Hz
    • Duty Cycle - 10%
    • Black lead @ Battery Negative Post
    • Red lead @ Signal circuit terminal 2
  11. Verify the scan tool parameter: Intermediate Speed Sensor Direction = Reverse
    • If not the specified state 

      Replace the component: K71 Transmission Control Module

    • Go to next step: If the specified state 
  12. Remove - EL-38522 Variable Signal Generator
  13. Connect the electrical connector: X1 @ T12 Automatic Transmission
  14. Ignition/Vehicle - Off
  15. Remove the component: Automatic Transmission Fluid Pan
  16. Disconnect the electrical connector: B14DA Automatic Transmission Intermediate Speed Sensor 1
  17. Ignition - On/Vehicle - In Service Mode
  18. 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 
  19. Ignition/Vehicle - Off
  20. Install - EL-38522 Variable Signal Generator
    • Voltage - 5 V
    • Frequency - 5 kHz
    • Duty Cycle - 10%
    • Black lead @ Battery Negative Post
    • Red lead @ Signal circuit terminal 1
  21. Ignition - On/Vehicle - In Service Mode
  22. Verify the scan tool parameter: Intermediate Speed Sensor = 5, 890 to 6, 090 RPM
    • If not between 5, 890 and 6, 090 RPM 

      Replace the component: Automatic Transmission Wiring Harness

    • Go to next step: If between 5, 890 and 6, 090 RPM 
  23. Test or replace the component: B14DA Automatic Transmission Intermediate Speed Sensor 1
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