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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1371 (Automatic Transmission - 6L80/6L90 - DTC P0218 To DTC P0963) >> DTC P071A >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2009 GMC Sierra, 2009 GMC Cab & Chassis Sierra, 2009 Chevrolet Silverado, and 2009 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition Off, transmission in Park, 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 Tow/Haul parameter 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.
  6. If the electrical circuit checks are OK and the tow/haul shift pattern is not occurring, there may be a mechanical/hydraulic condition that prevents tow/haul operation. Refer to Symptoms - Automatic Transmission .
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