P0174 - System Too Lean Bank 2
P0174 is a generic powertrain diagnostic trouble code indicating System Too Lean Bank 2. It relates to the Fuel & Air Metering system.
DTC Breakdown (SAE J2012)
| System | Powertrain (P) |
| Type | Generic |
| Subsystem | Fuel & Air Metering |
| Fault Index | 74 |
| Standard | SAE J2012 / ISO 15031-6 |
What does diagnostic code P0174 mean?
The engine control module has detected a lean fuel mixture on Bank 2, indicating an excess of air or a deficit of fuel entering the cylinders on that bank. The computer is maxing out its fuel correction trims to Bank 2.
Severity Level & Driveability Details
Severity: Moderate
Similar to P0171, it increases engine operating temperatures on Bank 2 cylinders, raising the risk of combustion chamber damage under heavy throttle.
Common Symptoms of P0174
- Engine stumble or hesitation under acceleration.
- Rough running engine at idle due to lean fuel trims on Bank 2.
- Lack of overall engine power.
- Random misfires on Bank 2 cylinders.
- Check engine light illuminated on the dashboard due to lean conditions on Bank 2.
Typical Causes for P0174
- Vacuum leaks on the Bank 2 side of the intake manifold or gasket surfaces.
- Dirty or failing Mass Air Flow (MAF) sensor.
- Low fuel pressure or fuel delivery restrictions on Bank 2 injectors.
- Leaking intake manifold gaskets on Bank 2.
Diagnostic and Troubleshooting Steps
Check fuel trim values on a scan tool. Look for vacuum leaks specifically around the Bank 2 runner ports using a smoke generator. Test fuel pressure under load to rule out a weak fuel pump.
Typical Repairs and Fixes
- Fixing Bank 2 vacuum leaks or cracked hoses.
- Replacing Bank 2 intake manifold gaskets.
- Cleaning or replacing the Mass Air Flow (MAF) sensor for Bank 2.
- Replacing a weak fuel pump or restricted fuel injectors.
Sensor Location & Parts Involved
The intake gaskets and vacuum lines are located on top of the engine block near the intake manifold on Bank 2.
Clearing Code & Recurrence
Reset the code using a scan tool and clear fuel trims to verify trims on Bank 2 return to normal.
Emissions & Smog Inspection Impact
Causes elevated cylinder temperatures on Bank 2, leading to high nitrogen oxide (NOx) tailpipe emissions.
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Related Diagnostic Codes
Sources & References
This diagnostic guide is compiled and verified against the following authority sources:
- CARB OBD Regulations Page
- EPA Fuel Trim Reference Guide
Frequently Asked Questions about P0174
What does the Bank 2 fuel trim lean code P0174 mean?
The engine control module has logged P0174 after detecting a lean air-fuel mixture on Bank 2, meaning there is too much air or too little fuel entering the cylinders.
Is it safe to drive with the Bank 2 fuel trim lean code P0174 active?
Yes, but avoid aggressive acceleration or heavy towing when Bank 2 runs lean.
How much does it cost to repair a Bank 2 fuel trim lean code P0174 fault?
Diagnostics for Bank 2 lean conditions cost $100-$150. Intake gaskets on Bank 2 are $250-$500; MAF sensor replacement is $150-$300; fuel pump is $400-$800.
What are the common causes of the Bank 2 fuel trim lean code P0174?
Trigger conditions for the Bank 2 fuel trim lean code P0174 include: Intake vacuum leaks (cracked PCV hoses, leaking manifold gaskets) on Bank 2., Dirty or failing Mass Air Flow (MAF) sensor., Weak fuel pump or clogged fuel filter reducing fuel delivery to Bank 2..
Can I clear the check engine light for Bank 2 fuel trim lean code P0174?
Reset the code using a scan tool and clear fuel trims to verify trims on Bank 2 return to normal.
Will the Bank 2 fuel trim lean code P0174 cause an inspection failure?
Causes elevated cylinder temperatures on Bank 2, leading to high nitrogen oxide (NOx) tailpipe emissions.