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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1048 (Automatic Transmission - 6L50/6L80/6L90 - DTC P0218 To DTC P0971) >> DTC P0851 or P0852 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2008 GMC Sierra, 2008 GMC Cab & Chassis Sierra, 2008 Chevrolet Silverado, and 2008 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 or Neutral, disconnect the transmission 16-way connector.
  2. Test for less than 1 ohm of resistance between the Park/Neutral signal circuit terminal 3 on the transmission side and the ground circuit terminal 5.
    • If greater than the specified range, test the signal circuit inside the transmission for an open/high resistance. If the circuit tests normal, test or replace the IMS.
  3. Ignition On, verify the scan tool parameter Park/Neutral displays In-gear.
    • If not the specified value, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM.
  4. Install a fused jumper between the signal circuit and ground. Verify the scan tool parameter Park/Neutral displays Park/Neutral.
    • 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 ECM.
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