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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 >> Tow/Haul Switch/Indicator Malfunction >> Circuit/System Testing

Circuit/System Testing

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  1. Ignition OFF and all vehicle systems OFF. Disconnect the harness connector at the S3 Transmission Shift Lever. It may take up to 2 min. for all vehicle systems to power down.
  2. Test for less than 5 Ω between the ground circuit terminal 2 and ground.
    • If 5 Ω or greater 
    1. Ignition OFF.
    2. Test for less than 2 Ω in the ground circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, repair the open/high resistance in the ground connection.
    • Go to next step: If less than 5 Ω 
  3. Ignition OFF.
  4. Test for less than 1 V on the signal circuit terminal 1 at the S3 Transmission Shift Lever harness connector.
    • If 1 V or greater 
    1. Ignition OFF.
    2. Disconnect the X3 harness connector at the K9 Body Control Module. Ignition ON.
    3. Test for less than 1 V on the signal circuit terminal 1 at the S3 Transmission Shift Lever harness connector and ground.
      • If 1 V or greater, repair the short to B+/Ignition in the signal circuit.
      • If less than 1 V, replace the K9 Body Control Module.
    • Go to next step: If less than 1 V 
  5. Ignition ON.
  6. Test for 10 - 13 V on the signal circuit terminal 1 at the S3 Transmission Shift Lever harness connector and ground.
    • If not between 10 - 13 V 
    1. Ignition OFF.
    2. Disconnect the X3 harness connector at the K9 Body Control Module.
    3. Test for less than 2 Ω in the signal circuit end to end.
      • If greater than 2 Ω, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K9 Body Control Module.
    • Go to next step: If between 10 - 13 V 
  7. Perform the Component Testing.
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