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Home/Cars/GMC/Sierra/T1XX (2019-Present)/how to fix P0171 code on GMC Sierra T1XX (2019-Present)

how to fix P0171 code on GMC Sierra T1XX (2019-Present)

GMC Sierra T1XX (2019-Present)

Error Codes
Severity: highDifficulty: mediumError Code: P01712-4 hours
4 min read
634 words

⚠️ Safety Warning

This issue requires immediate attention. If you are not experienced with automotive repairs, consult a professional mechanic. Working on critical systems can be dangerous.

Problem Statement

Learn how to diagnose and fix P0171 engine lean condition in GMC Sierra T1XX (2019-Present). Step-by-step guide with diagnostic procedures and repair instructions.

Error Code
P0171
Affected Component
Engine
Estimated Time
2-4 hours

Safety Warnings

  • ⚠Disconnect the battery before working on electrical systems.
  • ⚠Allow engine to cool before opening any engine components.

Symptoms

  • •Check engine light illuminated
  • •Rough idle or stalling
  • •Decreased power during acceleration
  • •Poor fuel economy
  • •Unusual engine noises (e.g., popping or backfiring)
  • •Increased emissions or failed emissions test

Diagnostic Steps

  1. 1Scan for error codes using an OBD-II scanner to confirm the P0171 code and check for any additional codes.
  2. 2Inspect the intake system for vacuum leaks, including hoses, gaskets, and the intake manifold.
  3. 3Check the Mass Air Flow (MAF) sensor for proper operation and cleanliness.
  4. 4Test the fuel pressure to ensure the fuel pump is providing adequate pressure.
  5. 5Inspect fuel injectors for clogs or electrical issues.
  6. 6Review the engine’s air filter condition; replace if it is dirty or clogged.

Solution

Solution

1. Preparation

  • Gather tools and parts needed for the repair.
  • Disconnect the negative battery terminal to prevent electrical shorts.
  • Allow the engine to cool completely before beginning work.

2. Inspect and Repair Vacuum Leaks

  • Sub-steps:
    1. Visually inspect all vacuum hoses for cracks or disconnections.
    2. Use compressed air or a smoke machine to identify any hidden leaks.
    3. Replace any damaged hoses or gaskets found during inspection.
  • Tools Required: Screwdrivers, pliers, smoke machine (optional).

3. Clean the MAF Sensor

  • Sub-steps:
    1. Locate the MAF sensor, typically found in the air intake duct.
    2. Disconnect the electrical connector and remove the sensor.
    3. Use MAF cleaner spray to clean the sensor element, avoiding physical contact.
    4. Allow it to dry before reinstalling.
  • Tools Required: Torx or socket set, MAF cleaner spray.
  • Safety Warnings: Do not use any other cleaner that may damage the sensor.

4. Check Fuel Pressure

  • Sub-steps:
    1. Connect a fuel pressure gauge to the fuel rail test port.
    2. Turn the ignition key to the "ON" position (do not start the engine) and observe the pressure reading.
    3. Compare the reading with the manufacturer’s specifications (typically around 55-62 psi for most GM vehicles).
    4. If pressure is low, check the fuel pump and filter for issues.
  • Tools Required: Fuel pressure gauge.

5. Inspect and Test Fuel Injectors

  • Sub-steps:
    1. Remove the engine cover if necessary to access the fuel injectors.
    2. Check the electrical connections to each injector for damage.
    3. Use a multimeter to test the resistance of the injectors, comparing with manufacturer specifications.
    4. If an injector is faulty, replace it.
  • Tools Required: Multimeter, socket set.
  • Safety Warnings: Relieve fuel system pressure before disconnecting fuel lines.

Verification

After completing the repair, verify that the issue has been resolved:

  • ✓Test the affected component to ensure it functions correctly
  • ✓Check for any error codes or warning lights
  • ✓Monitor the vehicle for a few days to ensure the issue does not recur

Prevention Tips

To prevent this issue from occurring again:

  • •Follow the manufacturer's recommended maintenance schedule
  • •Address warning signs early before they develop into major issues
  • •Use quality parts and fluids recommended for your vehicle
  • •Keep detailed records of all repairs and maintenance

Tools & Equipment Required

  • •OBD-II scanner
  • •Screwdrivers
  • •Pliers
  • •Multimeter
  • •Fuel pressure gauge
  • •Smoke machine (optional)
  • •MAF cleaner spray

Parts Required

  • •Replacement vacuum hoses and gaskets (if needed)
  • •MAF sensor cleaner
  • •Fuel injectors (if faulty)

Additional Information

Error Code
P0171
Affected Component
Engine
Estimated Time
2-4 hours
Difficulty
medium
Severity
high
Tools Required
7 items
Parts Required
3 items

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