how to diagnose the P0171 code in 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 necessary for the repair.
• Disconnect the negative battery terminal to ensure safety.

2. Inspect and Seal Air Leaks

• Tools Required: Screwdriver, hose clamps, vacuum gauge.
• Sub-steps:
  1. Visually inspect all vacuum lines and intake hoses for cracks or disconnections.
  2. Use a vacuum gauge to test for leaks in the intake manifold.
  3. Seal any leaks found with appropriate silicone sealant or replace damaged hoses.

3. Clean the MAF Sensor

• Tools Required: MAF sensor cleaner, soft cloth.
• Sub-steps:
  1. Disconnect the MAF sensor's electrical connector.
  2. Carefully remove the MAF sensor from the air intake.
  3. Spray the MAF sensor with MAF sensor cleaner, avoiding contact with the sensor wire.
  4. Allow the sensor to dry completely before reinstallation.

4. Check and Adjust Fuel Pressure

• Tools Required: Fuel pressure gauge.
• Sub-steps:
  1. Connect the fuel pressure gauge to the fuel rail test port.
  2. Turn the ignition key to the "ON" position (without starting the engine) to check the fuel pressure.
  3. Refer to the manufacturer's specifications for acceptable fuel pressure levels.
  4. If pressure is low, inspect the fuel pump and filter for issues.

5. Inspect and Replace Oxygen Sensors (if necessary)

• Tools Required: Oxygen sensor socket, ratchet.
• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors.
  2. Disconnect the electrical connectors and remove the sensors.
  3. Install new oxygen sensors and reconnect the electrical connectors.