Fuel mixture too lean
P0174
System Too Lean (Bank 2)
The engine is getting too much air or not enough fuel, and the computer has run out of room to correct it. On a V engine, P0171 and P0174 together usually point to something both banks share: a vacuum leak, the mass air flow sensor or fuel pressure.
Fix it soon
Can I keep driving? For a short while, gently. Have it checked in the next few days, and stop if the car feels, sounds or smells different. A lean engine runs hot inside. Left for long, it can misfire and damage the catalytic converter or the engine.
What the words mean
- Bank 2 is the side of a V engine that doesn't have cylinder 1.
Common causes
- A vacuum leak (a cracked hose or intake gasket)
- A dirty mass air flow sensor
- A weak fuel pump or clogged fuel filter
- A leaking PCV valve or hose
- Dirty or clogged injectors
Listed roughly from most to least likely. The same code can have different causes on different cars.
What to do
- Listen for a hiss with the engine running and check the vacuum hoses.
- Clean the mass air flow sensor with the proper cleaner.
- Have fuel pressure checked if the first two don't fix it.
General guidance. Your owner's manual wins. If a red warning light is on or the car drives differently, stop safely and get help.
Related codes
Track this automatically in Tagwell Auto
Tagwell Auto keeps your car's service dates and mileage, so when a code shows up you know what was done last. With a Bluetooth reader for the car's diagnostic port (called OBD-II), the phone app can read the code itself.