P0174

System Too Lean Bank 2

Fuel & air metering Generic OBD-II High

What it means

P0174 means the engine control module has detected too much air or too little fuel in the bank 2 cylinders — the mixture is running lean. The most common cause is unmetered air from a vacuum leak or a dirty mass airflow sensor, though weak fuel delivery can also be to blame. A sustained lean mixture raises combustion temperature and can lead to misfires.

High

Can I keep driving? Usually drivable short-term, but a persistently lean mixture raises combustion temperatures and can cause misfires, so diagnose it before long trips.

Real-world scan data

Seen in

899

scans in the past year

Found in

0.1%

of scans

0.2%

of scans that found faults

Appears alongside · share of P0174 scans

P0171in 67.2% of scans

P0300in 16.7% of scans

P1000in 15.7% of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

Check-engine light on
Rough idle, hesitation, or occasional misfire on acceleration
Reduced power and sluggish performance
Slightly worse fuel economy

Common causes

Most likely first

Vacuum or intake leak letting in unmetered air (most common)Likely
Dirty or failing mass airflow (MAF) sensorCommon
Low fuel delivery — clogged filter, weak pump, or low pressureCommon
Failing upstream oxygen sensor reporting a false lean signalLess often
Exhaust leak ahead of the O2 sensor pulling in airLess often
Weak or partially clogged fuel injectors on bank 2Less often

How to diagnose & fix

Work through it in order

Read freeze-frame data, then smoke-test the intake for vacuum leaks — the usual cause.
Inspect and clean the MAF sensor; check the air intake boot for cracks.
Check fuel pressure and the fuel filter to rule out lean-from-starvation.
Review live O2 and fuel-trim data to confirm the bank 2 lean condition.
Inspect the exhaust manifold and gaskets near the sensor for leaks.
If trims are still lean, test the injectors. Clear and re-test.

FAQ

Quick answers

Is it safe to drive with P0174?+

For short trips usually, but don't ignore it — a lean mixture runs hot and can trigger misfires that damage the catalytic converter over time.

Can I just clear P0174?+

It will come back within a drive cycle or two until the vacuum leak, MAF, or fuel-delivery cause is repaired.

Read & clear P0174 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX