AutoCodes – GMC – P0171 2018 GMC Sierra

P0171 2018 GMC Sierra Code - Fuel Trim System Lean Bank 1

Quick Answer

The Engine Control Module (ECM) controls a Closed Loop air/fuel metering system to provide the best possible combination of drivability, fuel economy, and emission control. Common causes include Dirty or Restricted Air Filter, Dirty or Faulty Mass Air Flow (MAF) Sensor, Intake Air Leaks. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P0171 2018 GMC Sierra indicates Fuel Trim System Lean Bank 1.
Common causes: Common causes include Dirty or Restricted Air Filter, Dirty or Faulty Mass Air Flow (MAF) Sensor, Intake Air Leaks.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 470

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jul 23, 2023

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0171 2018 GMC Sierra Description

The Engine Control Module (ECM) controls a Closed Loop air/fuel metering system to provide the best possible combination of drivability, fuel economy, and emission control. The ECM monitors the Heated Oxygen Sensor (HO2S) signal voltage and adjusts the fuel delivery based on the signal voltage while in Closed Loop. A change made to the fuel delivery changes the long and short-term fuel trim values. The short-term fuel trim values change rapidly in response to the HO2S signal voltages. These changes fine-tune the engine fueling. The long-term fuel trim values change in response to trends in the short-term fuel trim. The long-term fuel trim makes coarse adjustments to fueling to re-center and restore control to short-term fuel trim. The ideal fuel trim values are around 0 %. A positive fuel trim value indicates that the ECM is adding fuel to compensate for a lean condition. A negative fuel trim value indicates that the ECM is reducing the amount of fuel to compensate for a rich condition. The Diagnostic Trouble Code (DTC) will be set when the average long-term fuel trim weighted average value is greater or less than a calibrated value.

OBDII Code P0171 2018 GMC Sierra - Fuel Trim System Lean Bank 1 - AutoCodes.com — P0171 2018 GMC Sierra Code - Fuel Trim System Lean Bank 1

What does this mean?

What are the Possible Causes of the DTC P0171 2018 GMC Sierra?

Dirty or Restricted Air Filter
Dirty or Faulty Mass Air Flow (MAF) Sensor
Intake Air Leaks
Exhaust Gas Leaks
Fuel Contamination
Faulty or Clogged Fuel Injectors
Faulty Front Heated Oxygen Sensor
Ignition Misfiring
Low Fuel Pressure
Positive Crankcase Ventilation (PCV) Hose Leaks
Engine Control Temperature (ECT) inaccurate readings

How to Fix the DTC P0171 2018 GMC Sierra?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What does this mean?

Code Tech Notes

The P0171 code means that more air than gasoline is detected in the exhaust gases exiting the combustion chamber. If the P0171 is set in along with the P0174 code, it is highly likely that the problem is caused by an intake leak. If there are no intake leaks, the next step is to replace the air filter and clean the Mass Air Flow (MAF) Sensor. If the problem persists the MAF or Front Heated Oxygen (O2) Sensor will need to be replaced.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0171 2018 GMC Sierra code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P0171 2018 GMC Sierra Code

1. What does OBDII code P0171 on a 2018 GMC Sierra mean?

This code indicates a lean condition in the fuel trim system on Bank 1 of the engine, specifically indicating that there is too much air and not enough fuel in the air-fuel mixture.

2. What are the common symptoms of OBDII code P0171 on a 2018 GMC Sierra?

Common symptoms include rough idling, loss of power, hesitation or stumbling during acceleration, poor fuel economy, and possibly a check engine light illumination.

3. What are the possible causes of OBDII code P0171 on a 2018 GMC Sierra?

Potential causes include a vacuum leak, faulty oxygen sensor, dirty or clogged fuel injectors, a malfunctioning mass airflow sensor, low fuel pressure, or a faulty PCV valve.

4. How can I diagnose the OBDII code P0171 on a 2018 GMC Sierra?

Diagnosis typically involves using a scan tool to monitor live data from the oxygen sensors, fuel trims, and other relevant sensors to identify the underlying issue causing the lean condition.

5. Can a dirty air filter trigger OBDII code P0171 on a 2018 GMC Sierra?

Yes, a dirty or clogged air filter can disrupt the air-fuel mixture ratio, leading to a lean condition and triggering the P0171 trouble code.

6. What are some basic repair tips for addressing OBDII code P0171 on a 2018 GMC Sierra?

Start by checking for any obvious vacuum leaks, inspecting the air intake system for leaks or restrictions, cleaning or replacing the air filter, and ensuring all sensors are functioning correctly.

7. Is it safe to continue driving with OBDII code P0171 on a 2018 GMC Sierra?

It is not recommended to ignore this code and continue driving, as a lean condition can lead to potential engine damage over time. It's best to address the underlying issue promptly.

8. Can a bad fuel pump cause OBDII code P0171 on a 2018 GMC Sierra?

Yes, a failing fuel pump can result in insufficient fuel delivery, causing a lean condition and triggering the P0171 trouble code.

9. How much does it typically cost to repair OBDII code P0171 on a 2018 GMC Sierra?

The cost of repairs can vary depending on the specific cause of the lean condition, but it may range from a simple fix like replacing a sensor to more involved repairs like addressing a vacuum leak or fuel system issue.

10. Should I reset the trouble code after repairing OBDII code P0171 on a 2018 GMC Sierra?

Yes, after making the necessary repairs, it is advisable to clear the trouble code using a scan tool to reset the Check Engine Light and monitor for any recurring issues.