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 necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical issues.
• Allow the engine to cool before starting work.

2. Inspect and Repair Vacuum Leaks

• Tools Required: Vacuum gauge, hose clamps, basic hand tools
• Use a vacuum gauge to check for leaks. If a leak is found:
  • Tighten or replace any loose or damaged hoses.
  • Replace any vacuum lines that show signs of wear or damage.

3. Test and Replace Fuel Components

• Tools Required: Fuel pressure gauge, socket set
• Connect the fuel pressure gauge to the fuel rail and turn the ignition on (do not start the engine).
• Compare fuel pressure readings with manufacturer specifications:
  • If low, check the fuel pump, filter, and pressure regulator for faults. Replace as necessary.
  • If the fuel pressure is normal but the code persists, proceed to check the injectors.

4. Clean or Replace MAF Sensor

• Tools Required: MAF cleaner, screwdriver
• Remove the MAF sensor carefully from the intake.
• Spray the sensor with MAF cleaner and allow it to dry completely.
• Reinstall the MAF sensor, ensuring all connections are secure.

5. Inspect and Test Oxygen Sensors

• Tools Required: O2 sensor socket, multimeter
• Disconnect the oxygen sensor connectors and check resistance with a multimeter.
• Replace any sensors that are out of specification.

6. Reconnect Battery and Clear Codes

• Reconnect the negative battery terminal.
• Use an OBD-II scanner to clear the P0171 code and any other codes that were present.