how to fix P0171 code in GMC Sierra T1XX (2019-Present)

Learn how to diagnose and fix P0171 engine lean condition in GMC Sierra T1XX. Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the negative battery terminal to ensure safety.

2. Inspect and Repair Vacuum Leaks

• Sub-steps:
  • Visually inspect all vacuum hoses and connections for cracks or disconnections.
  • Use a smoke machine or propane torch (without igniting) to find leaks.
  • Replace any damaged hoses or repair connections as necessary.

3. Clean MAF Sensor

• Tools Required: MAF sensor cleaner
• Sub-steps:
  • Disconnect the MAF sensor electrical connector.
  • Remove the MAF sensor from the intake tubing.
  • Spray MAF sensor cleaner onto the sensor element, ensuring not to touch it.
  • Allow the sensor to dry completely before reinstalling it.

4. Inspect Fuel System

• Sub-steps:
  • Connect a fuel pressure gauge to the fuel rail test port.
  • Turn the ignition to the "ON" position without starting the engine to check pressure.
  • Compare the reading with manufacturer specifications (typically around 55-62 psi for most models).
  • If pressure is low, check the fuel filter and replace if necessary, and inspect the fuel pump for proper operation.

5. Clean Throttle Body

• Tools Required: Throttle body cleaner and a soft cloth
• Sub-steps:
  • Remove the throttle body from the intake manifold.
  • Spray throttle body cleaner inside the throttle body and wipe with a soft cloth to remove carbon buildup.
  • Reinstall the throttle body and reconnect the electrical connector.

6. Check and Replace Oxygen Sensors (if necessary)

• Sub-steps:
  • Review O2 sensor readings using the OBD-II scanner.
  • If readings are out of range, remove the faulty oxygen sensor using an O2 sensor socket.
  • Install the new oxygen sensor and reconnect any electrical connectors.