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Home >> Chevrolet >> 2021 >> Blazer L >> Repair and Diagnosis >> Transmission >> Automatic Trans >> Automatic Transmission - 9T50 (M3D), 9T60 (M3T) Or 9T65 (M3V) - Diagnostic Information And Procedures >> Diagnostic Information and Procedures >> DTC P171A-P171C >> Circuit/System Testing

Circuit/System Testing

  1. Ignition/Vehicle - Off
  2. Disconnect the electrical connector: B280 Automatic Transmission Accumulator Solenoid Valve
  3. Connect a test lamp between the test points: Control circuit terminal 1 & 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.

    • If the test lamp is always Off 
    1. Ignition/Vehicle - Off & Remove - Test lamp
    2. Disconnect the electrical connector: K71 Transmission Control Module
    3. Test for infinite resistance between the test points: Control circuit terminal 1 @ 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: Control circuit terminal 1 @ Component harness & Terminal 33 @ 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 the test lamp is always On 
    1. Ignition/Vehicle - Off & Remove - Test lamp
    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: Control circuit terminal 1 @ 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 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. Test for less than 2 ohms between the test points: Control circuit terminal 2 @ Component harness & Terminal 24 @ Control module harness
    • If 2 ohms or greater 

      Repair the open/high resistance in the circuit.

    • Go to next step: If less than 2 ohms 
  10. Test for infinite resistance between the test points: Control circuit terminal 2 & Ground
    • If less than infinite resistance 

      Repair the short to ground on the circuit.

    • Go to next step: If infinite resistance 
  11. Ignition - On / Vehicle - In Service Mode
  12. Test for less than 1 V between the test points: Control circuit terminal 2 & Ground
    • If 1 V or greater 

      Repair the short to voltage on the circuit.

    • Go to next step: If less than 1 V 
  13. Ignition/Vehicle - Off
    14. NOTE:

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

  14. Test for 17 to 19 ohms between the test points: Control terminal 1 & Control terminal 2
    • If not between 17 and 19 ohms 

      Replace the component: B280 Automatic Transmission Accumulator Solenoid Valve

    • Go to next step: If between 17 and 19 ohms 
  15. 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: B280 Automatic Transmission Accumulator Solenoid Valve

    • Go to next step: If infinite resistance 
  16. Replace the component: K71 Transmission Control Module
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