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 vehicle battery to ensure safety.
• Allow the engine to cool down.

2. Inspect and Repair Vacuum Leaks

• Tools Required: Vacuum gauge, hose clamps, and silicone sealant.
• Check all vacuum hoses connected to the intake manifold for cracks or disconnections.
• If any leaks are found, replace or reattach the hoses. Use silicone sealant on any gaskets that show signs of wear.

3. Clean or Replace MAF Sensor

• Tools Required: MAF cleaner and a Torx screwdriver.
• Remove the MAF sensor from the air intake duct.
• Spray the MAF sensor with MAF cleaner and allow it to dry. Do not touch the sensor wires.
• Reinstall the sensor securely.

4. Check and Repair Fuel System

• Tools Required: Fuel pressure gauge, socket set.
• Connect the fuel pressure gauge to the fuel rail to check for proper pressure according to the manufacturer specifications (typically 55-62 psi for Sierra).
• If the pressure is low, check the fuel pump and fuel filter; replace as necessary.
• Inspect fuel injectors for proper operation; clean or replace if clogged.

5. Inspect and Replace Oxygen Sensor (if necessary)

• Tools Required: O2 sensor socket and torque wrench.
• Remove the upstream oxygen sensor from the exhaust manifold.
• Inspect the sensor for damage; replace if necessary.
• Install the new oxygen sensor and torque it to manufacturer specifications (typically 30 lb-ft).

6. Reassemble and Clear Codes

• Reconnect the battery and all components removed during repair.
• Start the engine and allow it to reach operating temperature.
• Use the OBD-II scanner to clear the P0171 code.