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

Learn how to diagnose and fix P0171 engine too 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.
• Allow the engine to cool.

2. Inspect and Repair Vacuum Leaks

• Tools Required: Vacuum gauge, hose clamps, basic hand tools.
• Visually inspect all vacuum hoses connected to the intake manifold.
• Use a vacuum gauge to check for leaks; if a leak is found, replace the affected hose(s).

3. Check and Clean MAF Sensor

• Tools Required: MAF sensor cleaner, screwdriver.
• Remove the MAF sensor from the air intake duct.
• Spray MAF sensor cleaner on the sensing elements; do not touch them directly.
• Reinstall the MAF sensor ensuring a secure fit.

4. Test Fuel Pressure

• Tools Required: Fuel pressure gauge.
• Connect the fuel pressure gauge to the fuel rail's test port.
• Turn the ignition key to the "ON" position (do not start) and check the fuel pressure reading; it should meet the manufacturer's specifications (usually around 55-62 psi for many GM models).
• If the pressure is low, inspect the fuel pump and fuel filter for issues.

5. Inspect and Clean Fuel Injectors

• Tools Required: Fuel injector cleaning kit or professional cleaning service.
• Remove the fuel injectors from the fuel rail.
• Use a fuel injector cleaning kit to clean the injectors or take them to a professional service for cleaning.
• Reinstall the injectors ensuring all O-rings are intact.

6. Reassemble and Clear Codes

• Reconnect all components that were removed.
• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0171 code.
• Start the engine and allow it to idle, monitoring for any recurring issues.