AutoCodes – Hummer – P0174 Hummer

P0174 Hummer Code - Fuel Trim System Lean Bank 2

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: P0174 Hummer indicates Fuel Trim System Lean Bank 2.
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 14,078

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 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 P0174 Hummer 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 P0174 Hummer - Fuel Trim System Lean Bank 2 - AutoCodes.com — P0174 Hummer Code - Fuel Trim System Lean Bank 2

What does this mean?

What are the Possible Causes of the DTC P0174 Hummer?

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

How to Fix the DTC P0174 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

The P0174 code means that more air than gasoline is detected in the exhaust gases exiting the combustion chamber. If the P0174 is set in along with the P0171 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.

Click Here to Learn What is Bank 1 and Bank 2

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 P0174

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0174 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.

Need more information about the P0174 Hummer code?

Need more information on how to fix the P0174 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 P0174 Hummer Code

1. What are the common symptoms of OBDII code P0174 in a Hummer?

- Common symptoms include rough idling, engine hesitation, loss of power, increased fuel consumption, and the illumination of the check engine light.

2. What does the OBDII code P0174 indicating a "Fuel Trim System Lean Bank 2" mean in a Hummer?

- This code indicates that the engine control module has detected a lean condition in the fuel mixture on bank 2 of the engine, which can lead to drivability issues.

3. What are the possible causes of OBDII code P0174 in a Hummer?

- Common causes include a vacuum leak, faulty oxygen sensor, fuel delivery issues, intake air leaks, clogged fuel injectors, or a malfunctioning mass airflow sensor.

4. How can I diagnose the OBDII code P0174 in my Hummer?

- Diagnosing this code typically involves inspecting for vacuum leaks, testing oxygen sensors, checking fuel pressure, examining intake components, and using a scan tool to monitor fuel trims.

5. Can driving with OBDII code P0174 in a Hummer cause further damage?

- Continuing to drive with this code may lead to decreased fuel efficiency, potential damage to the catalytic converter, and ultimately affect the engine's performance.

6. How can I repair OBDII code P0174 in my Hummer?

- Repair options may include fixing vacuum leaks, replacing faulty oxygen sensors, cleaning or replacing fuel injectors, addressing intake air leaks, and ensuring proper fuel delivery.

7. Is it safe to reset the check engine light after repairing OBDII code P0174 in a Hummer?

- Yes, it is safe to reset the check engine light after repairing the issue. However, it is recommended to confirm that the problem has been resolved before doing so.

8. How long does it take to fix OBDII code P0174 in a Hummer?

- The time needed to fix this code can vary depending on the specific cause. Simple repairs like fixing a vacuum leak may take a short time, while diagnosing and replacing faulty components can take longer.

9. Should I attempt to repair OBDII code P0174 in my Hummer myself?

- If you have the necessary tools, experience, and knowledge, you can attempt to repair this code yourself. Otherwise, it may be best to consult a professional mechanic for accurate diagnosis and repair.

10. Will OBDII code P0174 cause my Hummer to fail an emissions test?

- Yes, if left unresolved, OBDII code P0174 can cause your Hummer to fail an emissions test due to the lean fuel mixture affecting emissions levels.