OBD-II Code P0174 — What It Means & How to Fix It

What Does This Error Mean?

P0174 means your engine is running too lean on Bank 2. Too lean means there's too much air and not enough fuel in the combustion mixture. Your car's computer has been adding extra fuel to compensate, but it's reached its limit. You may notice rough idle, hesitation, surging, or poor acceleration. If you also have P0171 (lean on Bank 1), the problem likely affects the entire engine.

Affected Models

All vehicles with V6/V8 engines 1996+
Common in Ford F-150
Common in BMW 3 Series
Common in Chevrolet Silverado
Common in Nissan Pathfinder

Common Causes

Vacuum leak on the Bank 2 side of the intake manifold
Dirty or failing mass airflow sensor giving incorrect readings
Clogged or failing fuel injectors on Bank 2 not delivering enough fuel
Weak fuel pump not maintaining enough pressure under load
Cracked or leaking intake manifold gasket on the Bank 2 side

How to Fix It

Check if you also have P0171 stored. If both codes are present, the problem affects the whole engine — think MAF sensor, fuel pump, or a large vacuum leak. If only P0174 appears, the problem is specific to Bank 2.

Bank 2 is the side of the engine opposite cylinder 1. Check your owner's manual to identify which side.
Inspect for vacuum leaks around the Bank 2 side of the intake manifold. Listen for hissing sounds and check all vacuum hoses, the PCV valve, and the brake booster hose.

Spray carburetor cleaner around vacuum connections while idling. If the RPM changes, you found the leak.
Clean or replace the mass airflow sensor. A dirty MAF sensor is a very common cause of lean codes. Use dedicated MAF sensor cleaner spray — never use other cleaners.

If the MAF sensor is bad, you'll typically see lean codes on both banks, not just Bank 2.
Check fuel pressure with a fuel pressure gauge. Low pressure means the pump can't keep up or the fuel filter is clogged. Compare your reading to the spec in your service manual.

Many auto parts stores will lend you a fuel pressure gauge for free. Normal pressure is usually 40-60 PSI depending on the vehicle.
If the vacuum and fuel systems check out, consider having the fuel injectors tested or cleaned. A partially clogged injector on Bank 2 can cause a lean condition on that bank only.

Professional injector cleaning costs $50-$100 and can restore proper spray pattern and flow.

When to Call a Professional

If basic checks don't resolve the lean condition, a mechanic can do advanced diagnostics. They can perform a smoke test to find hidden vacuum leaks. Fuel pressure and injector flow tests can identify fuel delivery problems. Expect to pay $100-$200 for diagnosis. Repairs range from $50 for a vacuum hose to $800+ for intake manifold gaskets or fuel injectors.

Frequently Asked Questions

What does 'too lean' mean?

Your engine needs a precise mix of air and fuel to run properly. The ideal ratio is about 14.7 parts air to 1 part fuel. Too lean means there's more air than there should be. Or not enough fuel is being delivered. Either way, combustion isn't happening as efficiently as it should.

What is Bank 2?

On V6 and V8 engines, cylinders are arranged in two rows called banks. Bank 1 is the side with cylinder number 1. Bank 2 is the opposite side. On inline 4-cylinder engines, there's only one bank. So P0174 typically only appears on V6, V8, or other multi-bank engines.

Can a dirty air filter cause P0174?

A dirty air filter alone usually won't cause a lean code. It actually restricts airflow, which would make things richer, not leaner. However, a damaged or improperly seated air filter can let unfiltered air in. This can contaminate the MAF sensor and cause incorrect readings. Always make sure the air filter is properly installed and sealed.