how to troubleshoot P0171 code on GMC Sierra T1XX (2019-Present)

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

Solution

1. Preparation

• Gather tools: OBD-II scanner, multimeter, fuel pressure gauge, socket set, and a cleaning solution for the MAF sensor.
• Ensure the vehicle is on a flat surface with the engine off and cool before starting.

2. Inspect and Repair Air Intake System

• Sub-steps:
  1. Visually inspect all vacuum hoses for cracks or disconnections.
  2. Use a smoke machine or carburetor cleaner to identify leaks in the intake manifold or hoses.
  3. Replace any damaged hoses or gaskets as necessary.

3. Clean MAF Sensor

• Sub-steps:
  1. Disconnect the electrical connector from the MAF sensor.
  2. Carefully remove the MAF sensor from the air intake duct.
  3. Spray MAF cleaner onto the sensor element without touching it.
  4. Allow it to dry before reinstalling.

4. Test Fuel Pressure

• Sub-steps:
  1. Locate the fuel pressure test port on the fuel rail.
  2. Connect the fuel pressure gauge to the port.
  3. Turn the ignition to the "on" position without starting the engine and observe the pressure reading.
  4. If the pressure is below manufacturer specifications, check the fuel pump and filter for issues.

5. Inspect Fuel Injectors

• Sub-steps:
  1. Remove the fuel rail to access the injectors.
  2. Use a multimeter to test the resistance of each injector.
  3. Clean the injectors using an appropriate fuel injector cleaner or replace them if faulty.

6. Check Throttle Body

• Sub-steps:
  1. Remove the intake duct connected to the throttle body.
  2. Inspect the throttle body for carbon buildup and clean it using throttle body cleaner.
  3. Ensure the throttle plate opens and closes smoothly.