AutoCodes – Hummer – P0171 Hummer

P0171 Hummer Code - Fuel Trim System Lean Bank 1

Quick Answer

The Engine Control Module (ECM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. Common causes include Intake air leaks, Faulty front heated oxygen sensor, Ignition misfiring. 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 Hummer indicates Fuel Trim System Lean Bank 1.
Common causes: Common causes include Intake air leaks, Faulty front heated oxygen sensor, Ignition misfiring.
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 46,790

How popular is this code, among other codes? Medium

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 Aug 21, 2022

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

The Engine Control Module (ECM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. Fuel delivery is controlled differently during Open Loop and Closed Loop. During Open Loop, the ECM determines fuel delivery based on sensor signals without heated oxygen sensor (HO2S) input. During Closed Loop, the ECM adds HO2S inputs to calculate the short and long term fuel trim (FT) adjustments. If the HO2S indicates a lean condition, the fuel trim values will be above 0 percent. If the HO2S indicates a rich condition, the FT values will be below 0 percent. The short term FT values change rapidly in response to the HO2S voltage signals. The long term FT makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1.

OBDII Code P0171 Hummer - Fuel Trim System Lean Bank 1 - AutoCodes.com — P0171 Hummer Code - Fuel Trim System Lean Bank 1

What does this mean?

What are the Possible Causes of the DTC P0171 Hummer?

Intake air leaks
Faulty front heated oxygen sensor
Ignition misfiring
Faulty fuel injectors
Exhaust gas leaks
Incorrect fuel pressure
Lack of fuel
Faulty Mass Air Flow (MAF) sensor
Incorrect Positive Crankcase Ventilation (PCV) hose connection

How to Fix the DTC P0171 Hummer?

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

If the P0171 is combined with the P0174 code, it's very 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 air flow meter. If the problem persists the front oxygen (O2) sensor may need to be replaced.
The P0171 code could also be caused may be caused by one or more of the following: debris on the MAF sensor causing an incorrect reading, improper oil level, low or high fuel pressure, or Engine Control Temperature (ECT) Sensor reading inaccurate.

There is a Factory Service Bulletin for the following HUMMER models:
2003-2008 HUMMER H2
2006-2008 HUMMER H3
2003-2008 HUMMER Factory Service Bulletin OBDII Code P0171

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0171 Hummer 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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Need more information on how to fix the P0171 Hummer code? Get Access to Factory Service Manuals

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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 Hummer Code

1. What are the common symptoms of OBDII code P0171 on a Hummer?

- Common symptoms include rough idling, loss of power, engine hesitation, and an illuminated check engine light.

2. What does the OBDII code P0171 for a Hummer indicate?

- The code P0171 specifically indicates a lean fuel condition in the fuel trim system on Bank 1 of the engine.

3. What are the possible causes of OBDII code P0171 on a Hummer?

- Possible causes include a vacuum leak, faulty Mass Air Flow (MAF) sensor, fuel delivery issues, exhaust leaks, or a malfunctioning oxygen sensor.

4. How can I diagnose the OBDII code P0171 on my Hummer?

- Diagnosing the code may involve checking for intake leaks, inspecting the MAF sensor, testing the oxygen sensor, and verifying fuel pressure and injector operation.

5. Can a dirty air filter trigger the OBDII code P0171 on a Hummer?

- Yes, a dirty air filter can disrupt the air-fuel mixture and potentially lead to a lean condition triggering the code P0171.

6. Is it safe to continue driving my Hummer with the OBDII code P0171?

- It is not recommended to drive your Hummer with the code P0171 as it can cause damage to the engine and affect its performance.

7. How can I repair the OBDII code P0171 on my Hummer?

- Repair options may include fixing vacuum leaks, replacing the MAF sensor, addressing fuel system issues, repairing exhaust leaks, or replacing a faulty oxygen sensor.

8. Can a bad fuel pump cause the OBDII code P0171 on a Hummer?

- Yes, a failing fuel pump can lead to insufficient fuel delivery, causing the engine to run lean and triggering the code P0171.

9. Will resetting the check engine light eliminate the OBDII code P0171 on a Hummer?

- Resetting the check engine light may temporarily clear the code, but it will return if the underlying issue causing the lean condition is not resolved.

10. How important is it to address the OBDII code P0171 promptly on a Hummer?

- Addressing the code promptly is crucial to prevent potential engine damage, ensure optimal fuel efficiency, and maintain the overall performance of your Hummer.