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Home >> GMC >> 2006 >> Sierra 1500 HD, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1371 (Automatic Transmission - 6L80/6L90 - DTC P0218 To DTC P0963) >> DTC P0850-P0852 >> 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 or Neutral, disconnect the transmission 16-way connector.
  2. With the ignition On, test for 12 volts on pin 3 on the engine side of the transmission 16-way connector.
    • If not as specified, test the signal circuit for an open or short to ground. If the circuit tests normal, continue with testing.
    • If no open or short to ground is found, replace the ECM.
  3. Ignition OFF, transmission in Park, connect the transmission 16-way connector. With the ignition On, note any change with the scan tool Park/Neutral status.
    • If no status change was noted, test the signal circuit for a short to voltage.
    • If no short voltage is found and Park/Neutral status changed, test the manual shift shaft position switch for a short to ground.
    • If no short to ground is found, continue testing.
  4. Remove the transmission bottom fluid pan. Disconnect the manual shift shaft position switch connector from the control solenoid (w/body and TCM) valve assembly. Do not disconnect the transmission 16-way connector.
    • If this action has no effect on the scan tool parameter, replace the control solenoid (w/body and TCM) valve assembly.
    • If the Park/Neutral status changed, replace the manual shift shaft position switch.
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