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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1380 (Automatic Transmission - 6L80/6L90 - DTC P0967 To DTC P2764) >> DTC P0989 or P0990 >> Circuit/System Verification

Circuit/System Verification

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. If there are any other transmission related DTCs set, diagnose those DTCs first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle .
  2. Perform the Control Solenoid Valve and Transmission Control Module Assembly Cleaning procedure to dislodge debris and free up valves.
  3. Engine idling, parking brake applied, range selector in D, command the Shift Transmission with a scan tool to achieve 2nd gear.
  4. Observe the suspect scan tool TFP Switch parameter while commanding the Shift Transmission with a scan tool to achieve 5th gear. Each TFP Switch parameter should toggle states, from High to Low or Low to High, between 2nd and 5th gear.
    • If the specified parameter does not toggle, replace the control solenoid (w/body and TCM) valve assembly.
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