LEMON Manuals: Even more car manuals for everyone
Home >> Chevrolet >> 2018 >> Suburban 3500 HD LT >> Repair and Diagnosis >> External Pages >> Different car >> Section 21 (Automatic Transmission - 10L80 (MF6) - Diagnostic Information And Procedures) >> Diagnostic Information And Procedures >> DTC P0721, P0722, P0723, P077C, P077D, P172A Or P172B: Output Speed Sensor >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2018 GMC Yukon XL, 2018 GMC Yukon, 2018 Chevrolet Tahoe, 2018 Cadillac Escalade ESV, and 2018 Cadillac Escalade. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition/Vehicle & All vehicle systems - Off
    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.
  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: 9V 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: 9V Reference circuit terminal 7 @Component harness & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • 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. Connect the electrical connector: X1 @ T12 Automatic Transmission Assembly
    2. Ignition/Vehicle - Off
    3. Disconnect the electrical connector: X1 @ T12 Automatic Transmission Assembly
    4. Disconnect the electrical connector: K71 Transmission Control Module
    5. Ignition - On / Vehicle - In Service Mode
    6. Test for less than 1 V between the test points: 9V 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. Connect the electrical connector: X1 @ T12 Automatic Transmission Assembly
  6. Ignition/Vehicle - Off
  7. Disconnect the electrical connector: X1 @ T12 Automatic Transmission Assembly
  8. Install EL-38522 Variable Signal Generator
    • Set the voltage to 5 V
    • Set the frequency to 300 Hz
    • Set the duty cycle to 50%
    • Black lead @ Ground
    • Red lead @ Signal circuit terminal 4
  9. Ignition - On / Vehicle - In Service Mode
  10. Verify the scan tool parameter:Transmission OSS = 256 to 276 RPM
    • If not between 256 and 276 RPM 
    1. Connect the electrical connector. X1 @ T12 Automatic Transmission Assembly
    2. Ignition/Vehicle - Off
    3. Disconnect the electrical connector: X1 @ T12 Automatic Transmission Assembly
    4. Disconnect the electrical connector:K71 Transmission Control Module
    5. Ignition - On / Vehicle - In Service Mode
    6. Test for less than 1 V between the test points:Signal circuit terminal 4 @ Component harness & Ground
      • If 1 V or greater - Repair the short to voltage on the circuit.
      • If less than 1 V
    7. Connect the electrical connector. X1 @ T12 Automatic Transmission Assembly
    8. Connect the electrical connector.K71 Transmission Control Module
    9. Ignition/Vehicle - Off
    10. Disconnect the electrical connector: X1 @ T12 Automatic Transmission Assembly
    11. Disconnect the electrical connector:K71 Transmission Control Module
    12. Test for infinite resistance between the test points:Signal circuit terminal 4 @ Component harness & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • If infinite resistance
    13. Test for less than 2 ohms between the test points:Signal circuit terminal 4 @ Component harness & Terminal 14 @ 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 256 and 276 RPM 
  11. Connect the electrical connector. X1 @ T12 Automatic Transmission Assembly
  12. Connect the electrical connector.K71 Transmission Control Module
  13. Ignition/Vehicle - Off
  14. Disconnect the electrical connector: X1 @ T12 Automatic Transmission Assembly
  15. Remove the component:Automatic Transmission Fluid Pan
  16. Connect the electrical connector. X1 @ T12 Automatic Transmission Assembly
  17. Disconnect the electrical connector:B14A Transmission Output Shaft Speed Sensor
  18. Ignition - On / Vehicle - In Service Mode
  19. 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 
  20. Ignition/Vehicle - Off
  21. Install the special tool: EL-38522  Variable Signal Generator
    • Set the voltage to 5 V
    • Set the frequency to 300 Hz
    • Set the duty cycle to 50 %
    • Black lead@Ground
    • Red lead@Signal circuit terminal 1
  22. Ignition - On / Vehicle - In Service Mode
  23. Verify the scan tool parameter:Transmission OSS = 256 to 276 RPM
    • If not between 256 and 276 RPM 

      Replace the component:Automatic Transmission Wiring Harness

    • Go to next step: If between 256 and 276 RPM 
  24. Test or replace the component:B14A Transmission Output Shaft Speed Sensor
scientia non olet · About LEMON Manuals