how to fix P0171 code on my 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 needed for repairs.
• Disconnect the negative battery terminal to prevent electrical issues.
• Allow the engine to cool before working on components.

2. Inspect and Repair Vacuum Leaks

• Sub-steps:

  1. Use a smoke machine to pressurize the intake system and identify leaks.
  2. Replace any damaged vacuum hoses or gaskets identified during inspection.

• Tools Required: Smoke machine, replacement hoses or gaskets.

3. Clean or Replace MAF Sensor

• Sub-steps:

  1. Locate the MAF sensor in the air intake duct.
  2. Disconnect the electrical connector and remove the sensor from the duct.
  3. Clean the MAF sensor using MAF cleaner spray; do not touch the sensor elements.
  4. If damaged, replace the MAF sensor with a new one.

• Tools Required: MAF cleaner spray, screwdriver.

4. Test and Repair Fuel System

• Sub-steps:

  1. Connect a fuel pressure gauge to the fuel rail and turn the ignition to the ON position (do not start the engine).
  2. Check that the fuel pressure is within manufacturer specifications (usually around 55-62 psi).
  3. If pressure is low, inspect the fuel pump, filter, and injectors for blockages or failure.
  4. Replace the fuel filter if necessary and consider replacing the fuel pump if it does not meet pressure specifications.

• Tools Required: Fuel pressure gauge, socket set, replacement fuel filter/pump if needed.

5. Clear Codes and Test Drive

• Sub-steps:

  1. Reconnect the negative battery terminal.
  2. Use the OBD-II scanner to clear the P0171 code.
  3. Start the engine and monitor for any check engine light reappearance.
  4. Test drive the vehicle to ensure proper engine performance and fuel economy.

• Tools Required: OBD-II scanner.