how to fix P0171 code on 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 battery to ensure safety while working on electrical components.

2. Inspect and Repair Vacuum Leaks

• Tools Required: Vacuum gauge, hose clamp pliers, wrench set.
• Use a vacuum gauge to check for leaks in the intake system.
• Visually inspect all hoses and joints. Replace any damaged or cracked hoses.
• Tighten or replace any loose clamps around the intake manifold and throttle body.

3. Clean the Mass Air Flow (MAF) Sensor

• Tools Required: MAF cleaner, soft brush (if needed).
• Locate the MAF sensor in the air intake path.
• Disconnect the electrical connector and remove the sensor from the housing.
• Spray the MAF cleaner onto the sensor elements and allow it to dry completely before reinstalling.

4. Check and Repair Fuel System

• Tools Required: Fuel pressure gauge, socket set.
• Connect the fuel pressure gauge to the fuel rail.
• Start the engine and monitor the fuel pressure. It should meet the manufacturer’s specifications (typically around 55-62 psi for GMC Sierra).
• If pressure is low, check the fuel pump, filter, and fuel lines for blockages or failures. Replace any faulty components.

5. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench set.
• Locate the upstream (pre-catalytic converter) oxygen sensor.
• Disconnect the electrical connector and use the O2 sensor socket to remove the sensor.
• Install the new oxygen sensor and reconnect the electrical connector.

6. Reconnect Battery and Clear Codes

• After completing repairs, reconnect the battery.
• Use an OBD-II scanner to clear the P0171 code from the ECM.