Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET2009AVALANCHE 6.0 Y, RWDREPAIR AND DIAGNOSISTRANSMISSIONAUTOMATIC TRANSAUTOMATIC TRANSMISSION - 6L80/6L90 - DTC P0218 TO DTC P0963DTC P0872 OR P0873CIRCUIT/SYSTEM VERIFICATION
2009 Chevrolet Avalanche 6.0 Y, RWD
Circuit/System Verification
2009 Chevrolet Avalanche 6.0 Y, RWDSECTION Circuit/System Verification
- If there are any other transmission related DTCs set, diagnose those DTCs first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle .
- Perform the Control Solenoid Valve and Transmission Control Module Assembly Cleaning procedure to dislodge debris and free up valves.
- Engine idling, parking brake applied, range selector in D, command the Shift Transmission with a scan tool to achieve 2nd gear.
- 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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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.