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Home >> Cadillac >> 2018 >> Escalade Base, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 19 (Automatic Transmission - 6L80 (MYC) Or 6L90 (MYD) - Diagnostic Information And Procedures) >> Diagnostic Information And Procedures >> DTC P071A: Transmission Tow Mode Switch Circuit >> 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 Chevrolet Suburban 3500 HD, and 2018 Chevrolet Suburban. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, transmission in Park. Disconnect the S3 transmission shift lever electrical connector.
  2. Ignition OFF, test for less than 1 Ω between terminal 2 on the S3 transmission shift lever vehicle harness connector and ground at the battery negative post.
    • If 1 Ω or greater 
    1. Ignition OFF.
    2. Test for less than 1 Ω in the ground circuit wire, end to end.
      • If 1 Ω or greater, repair the open/high resistance in the wire circuit.
      • If less than 1 Ω, repair the open/high resistance in the ground connection or the terminal connection at the S3 transmission shift lever.
    • Go to next step: If less than 1 Ω 
  3. Ignition ON, test for greater than 11 volts on the signal circuit terminal 1 on the S3 transmission shift lever vehicle harness connector and ground at the battery negative post.
    • If less than 11 volts 
    1. Ignition OFF.
    2. Test for less than 1 Ω in the signal circuit wire, end to end.
      • If 1 Ω or greater, repair the open/high resistance in the signal circuit wire.
      • If less than 1 Ω, repair the open/high resistance in either terminals on the signal circuit wire.
    • Go to next step: If greater than 11 volts 
  4. Ignition OFF, test for less than 3 ohms between terminal 1 and terminal 2 on the S3 transmission shift lever component harness connector while depressing the S74 Tow/Haul Mode switch button.
    • If greater than 3 Ω 

      Replace the S3 transmission shift lever assembly.

    • Go to next step: If less than 3 Ω 
  5. If all circuits test normal, replace the K9 body control module.
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