how to resolve 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 to prevent electrical shorts.
• Ensure the engine is cool before starting any work.

2. Inspect and Repair Vacuum Leaks

• Tools Required: Vacuum gauge, hose clamps, socket set
• Use a vacuum gauge to check for leaks. If the reading is low, inspect all hoses and connections.
• Replace any damaged hoses or gaskets found during inspection.

3. Clean or Replace MAF Sensor

• Tools Required: MAF cleaner, screwdriver
• Disconnect the MAF sensor wiring harness.
• Remove the MAF sensor from the intake using a screwdriver.
• Clean the sensor with MAF cleaner and allow it to dry completely. If damaged, replace with a new sensor.

4. Check Fuel System

• Tools Required: Fuel pressure gauge, socket set
• Connect a fuel pressure gauge to the fuel rail and check for proper fuel pressure as per manufacturer specifications (typically around 55-62 psi for GMC Sierra).
• Replace the fuel filter if needed, and ensure the fuel pump is functioning correctly.

5. Inspect and Test Oxygen Sensor

• Tools Required: Multimeter, O2 sensor socket
• Locate the oxygen sensor on Bank 1 and disconnect the wiring harness.
• Use a multimeter to check the sensor's voltage output (should fluctuate between 0.1 to 0.9 volts).
• Replace the oxygen sensor if it is faulty.

6. Reassemble and Reconnect

• Reinstall any components removed during the inspection and repair process.
• Reconnect the negative battery terminal.
• Clear the error codes using the OBD-II scanner.