P0174
Fix within a few daysYour engine is running too lean on Bank 2, meaning there's too much air or not enough fuel for proper combustion on that side of the engine.
Code P0174 means your engine is running lean on Bank 2. Common causes: Vacuum leaks (50%), MAF sensor (20%), low fuel pressure (15%). Drivability: Limit driving, fix within a few days. Repair cost: $50-$200 DIY, $150-$500 professional.
Can I Drive With P0174?
Limit driving, fix within a few days
Essential trips under 10 miles, avoid highways and heavy acceleration. Prolonged driving can cause engine damage.
Stop driving immediately if: Flashing Check Engine Light, significant loss of power, loud engine noises, or a strong burning smell.
Symptoms of P0174
- 1Check Engine Light is on
- 2Rough idle or engine hesitation
- 3Reduced engine power
- 4Poor fuel economy
- 5Engine stalling (less common)
Common Causes of P0174
Parts most likely causing this code, ranked by probability
Unmetered air entering the engine after the MAF sensor causes the computer to incorrectly reduce fuel delivery, leading to a lean condition.
50% of P0174 cases are fixed by repairing vacuum leaks
A dirty or faulty MAF sensor can report less air entering the engine than is actually present, causing the computer to inject insufficient fuel.
20% of P0174 cases are fixed by replacing or cleaning the MAF sensor
Low fuel pressure from a failing fuel pump or a clogged fuel filter starves the engine of fuel, leading to a lean condition across one or both banks.
15% of P0174 cases are fixed by addressing fuel pressure issues
One or more fuel injectors on Bank 2 can become clogged, restricting fuel flow to specific cylinders and causing a lean condition on that bank.
10% of P0174 cases are fixed by cleaning or replacing fuel injectors
A faulty Bank 2 upstream oxygen sensor can send incorrect voltage signals to the engine computer, falsely indicating a lean condition or failing to properly report an actual lean condition.
5% of P0174 cases are fixed by replacing the Bank 2 upstream oxygen sensor
Check These First (Before Buying Parts)
- Visually inspect all accessible vacuum hoses for cracks, disconnections, or loose clamps.
- Ensure your gas cap is tight and not damaged.
- Clean the Mass Air Flow (MAF) sensor with MAF cleaner.
How to Diagnose P0174
- 1Visually inspect all vacuum hoses, PCV valve, and intake manifold for cracks, loose connections, or signs of leaks.
- 2Clean the Mass Air Flow (MAF) sensor with a dedicated MAF sensor cleaner.
- 3Check fuel pressure at the fuel rail using a fuel pressure gauge to ensure it meets manufacturer specifications.
- 4Use an OBD-II scan tool to monitor live data, specifically short-term and long-term fuel trims for Bank 2, and compare them to Bank 1.
- 5Perform a smoke test on the intake system to pinpoint any hidden vacuum leaks.
- 6If fuel pressure is good, consider testing the fuel injectors on Bank 2 for proper spray pattern and flow.
P0174 on Popular Vehicles
Toyota Camry
2007-2024V6 models are prone to intake manifold gasket leaks and vacuum hose issues, which often trigger P0174. MAF sensor cleaning is also a common first step.
60% fixed by repairing vacuum leaks or cleaning/replacing MAF sensor
Ford F-150
2004-2024On V8 F-150s, P0174 is frequently linked to vacuum leaks from the PCV system (hoses, valve) or intake manifold. MAF sensor issues are also common.
65% fixed by repairing vacuum leaks or cleaning/replacing MAF sensor
Honda Accord
2003-2024V6 Accord models can experience P0174 due to intake manifold gasket leaks or issues with the PCV valve and its associated hoses. MAF sensor problems are also seen.
60% fixed by repairing vacuum leaks or cleaning/replacing MAF sensor
Frequently Asked Questions
What does P0174 mean?
P0174 indicates that the engine computer has detected a lean condition on Bank 2. This means there's too much air or not enough fuel in the air-fuel mixture for optimal combustion on the side of the engine that does not contain cylinder #1.
Can I drive with P0174?
Limit driving, fix within a few days. While your car might seem to run fine, a lean condition can cause engine damage, reduce fuel economy, and lead to more expensive repairs like a damaged catalytic converter if ignored.
Will P0174 clear itself?
No, P0174 will not clear itself. The engine computer will continue to detect the lean condition and keep the Check Engine Light on until the underlying problem is diagnosed and repaired. You will need to clear the code with a scan tool after the repair.
How do I fix P0174 myself?
Start by visually inspecting all vacuum hoses and the intake manifold for leaks. Clean your Mass Air Flow (MAF) sensor with MAF cleaner. If the code persists, you'll need an OBD-II scan tool to monitor fuel trims and potentially a smoke machine to find hidden vacuum leaks. Replacing a faulty MAF sensor or intake manifold gasket are common DIY fixes.
How much does it cost to fix P0174?
DIY repair costs range from $50 for a new vacuum hose or MAF sensor cleaner to $200 for a new MAF sensor or intake manifold gasket. Professional shop repairs typically cost $150 to $500, including diagnosis and parts.
P0174 keeps coming back - why?
If P0174 keeps returning, it means the root cause was not correctly identified or fully resolved. Common reasons for recurrence include missing a small vacuum leak, a partially clogged fuel injector, a failing fuel pump, or a misdiagnosed MAF sensor issue.
Will P0174 fail emissions/smog test?
Yes, P0174 will cause your vehicle to fail an emissions or smog test. The Check Engine Light being on is an automatic failure in most jurisdictions, and a lean condition directly impacts exhaust emissions.
What's the difference between P0174 and P0171?
P0174 indicates a lean condition on Bank 2, which is the side of the engine that does not contain cylinder #1. P0171 indicates a lean condition on Bank 1, the side of the engine that contains cylinder #1. Both codes point to similar issues but on different banks of a V-style engine.
P0174 on Toyota Camry?
On Toyota Camry V6 models, P0174 is frequently caused by vacuum leaks, especially from a cracked or deteriorated intake manifold gasket or PCV system hoses. A dirty MAF sensor is also a common culprit.
Questions to Ask Your Mechanic
Did you check for vacuum leaks using a smoke machine, especially around the intake manifold and PCV system?
Good answer: Yes, we performed a smoke test and found a leak at [specific location, e.g., the intake manifold gasket on Bank 2] or 'No, the system is sealed tight.'
What were the short-term and long-term fuel trim readings for Bank 2 at idle and under load?
Good answer: At idle, Bank 2 short-term fuel trim was [e.g., +25%] and long-term was [e.g., +18%]. Under load, they dropped to [e.g., +10% and +12%]. This indicates a vacuum leak that's more pronounced at idle.
Repair Cost Estimate
DIY Repair
Parts only
$50-$200
Shop Repair
Parts + labor
$150-$500
Save $100-$300 by doing it yourself
Difficulty
intermediate
Time
1-4 hours
Intermediate. While some initial checks and cleaning are beginner-friendly, proper diagnosis often requires an OBD-II scan tool to interpret live data and potentially specialized tools like a smoke machine or fuel pressure gauge.
Cost of Waiting
Ignoring P0174 can lead to severe engine damage from running too lean, including burnt valves, damaged pistons, and premature failure of your catalytic converter. A $50 vacuum hose fix now prevents a $1,200-$2,500 catalytic converter replacement or even more expensive engine repairs later.
While You're In There...
If you are addressing vacuum leaks, the PCV system is a common source and often requires replacement at similar mileage intervals.
If you are cleaning or replacing the MAF sensor, a dirty air filter can contribute to MAF issues and should be replaced to ensure proper airflow.
If you suspect an intake manifold leak, it's smart to replace all associated gaskets to prevent future leaks and ensure a complete seal.
Tools You'll Need
- OBD-II scan tool
- Basic hand tools (sockets, wrenches, screwdrivers)
- MAF sensor cleaner
- Vacuum hose pliers (optional)
- Fuel pressure gauge (for advanced diagnosis)
- Smoke machine (for advanced diagnosis)
P0174 is a very common engine code indicating a lean condition. Most repairs are straightforward and involve fixing vacuum leaks or addressing sensor issues. Addressing this quickly prevents more expensive damage to your engine or catalytic converter.
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Your Next Steps
Step 1: Visually inspect all vacuum hoses, the PCV valve, and the intake manifold for any obvious cracks, disconnections, or loose fittings. Tighten any loose clamps.
Step 2: Clean your Mass Air Flow (MAF) sensor using a dedicated MAF sensor cleaner. Allow it to dry completely before reconnecting.
Step 3: If the code persists, use an OBD-II scan tool to monitor live data, focusing on Bank 2 fuel trims. Consider performing a smoke test to definitively locate any hidden vacuum leaks.