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Home >> GMC >> 2006 >> Sierra 1500 HD, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1728 (Automatic Transmission - 4L60-E/4L65-E/4L70-E - Symptom Troubleshooting And Diagnosis) >> Tow/Haul Switch/Indicator Always On or Inoperative >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2010 GMC Sierra and 2010 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, transmission in PARK or NEUTRAL, disconnect the Tow/Haul switch connector.
  2. Test for less than 1 ohm of resistance between the Tow/Haul switch signal circuit terminal B and ground.
    • If greater than the specified range, test the ground circuit for an Open/High resistance.
  3. Ignition ON, verify the scan tool parameter Park/Neutral displays INACTIVE.
    • If not the specified value, test the signal circuit for a short to ground. If the circuit tests normal, replace the BCM.
  4. Install a fused jumper between the signal circuit and ground. Verify the scan tool parameter displays ACTIVE.
    • If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
  5. If all circuits test normal, replace the Tow/Haul switch.
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