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Home >> Cadillac >> 2018 >> Escalade Base, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 21 (Automatic Transmission - 8L90 (M5U) - Diagnostic Information And Procedures) >> Diagnostic Information And Procedures >> Tow/Haul Switch/Indicator Malfunction >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2018 Chevrolet Suburban 3500 HD. However, it is still accessible from the selected car via links, so may be relevant.
  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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