how to fix a check engine light on my GMC Sierra T1XX (2019-Present) for P0171?

Learn how to diagnose and fix P0171 code indicating engine running too lean in GMC Sierra T1XX. Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to ensure safety while working on the vehicle.
• Allow the engine to cool if it has been running.

2. Inspect and Repair Vacuum Leaks

• Tools Required: Vacuum gauge, hose clamps
• Instructions:
  1. Use a vacuum gauge to check for leaks in the intake manifold and vacuum lines.
  2. Replace any cracked or damaged hoses.
  3. Ensure that all connections are tight and secure.

3. Clean or Replace MAF Sensor

• Tools Required: MAF cleaner, screwdriver
• Instructions:
  1. Locate the MAF sensor in the air intake duct.
  2. Remove the sensor using a screwdriver.
  3. Clean the sensor with MAF cleaner and let it dry completely.
  4. Reinstall the sensor securely.

4. Test and Repair Fuel Delivery System

• Tools Required: Fuel pressure gauge, multimeter
• Instructions:
  1. Connect a fuel pressure gauge to the fuel rail to check the pressure against manufacturer specifications.
  2. If pressure is low, check the fuel pump and replace if necessary.
  3. Inspect fuel injectors for clogs or malfunctions and clean or replace as needed.

5. Inspect Throttle Body

• Tools Required: Throttle body cleaner, cloth
• Instructions:
  1. Remove the air intake duct to access the throttle body.
  2. Clean the throttle body using throttle body cleaner and a cloth, ensuring no debris is left behind.
  3. Reassemble all components securely.

6. Reset the Engine Control Module (ECM)

• Tools Required: OBD-II scanner
• Instructions:
  1. Reconnect the negative battery terminal.
  2. Use the OBD-II scanner to clear the P0171 code from the ECM.
  3. Start the engine and check for any reoccurring issues.