Parts
$20–400
P0174 — System Too Lean (Bank 2)
CAUTIONIs it safe to drive? Lean on Bank 2 (the side without cylinder 1). Same risks as P0171 — driveable but worth chasing.
What P0174 means
Too much air for the fuel on Bank 2. With P0171 also present, suspect a shared cause (intake leak, MAF, fuel supply) rather than one bank.
Most likely causes (in order)
- Vacuum / intake leak
- Dirty MAF (if both banks lean)
- Weak fuel pump / clogged filter
- Intake manifold gasket leak
Symptoms you might notice
- Rough idle
- Lean stumble
- Lower economy
What to check first
If P0171 AND P0174 are both set, it's almost never two separate leaks — look at the shared stuff: MAF, fuel pressure, a big central vacuum leak.
Repair cost & difficulty
Labor
0.5–3 hr
Difficulty
DIY-friendly