P0174 fault code: what it means

P0174: Bank 2 is running lean. Set together with P0171 it points to a cause common to both banks, like a MAF or big air leak.

Engine and gearbox (powertrain) · Costly if missed

Usual causes, most likely first

vacuum or intake air leak
dirty or faulty MAF sensor
low fuel pressure
exhaust leak before the bank 2 sensor

P0174 by make

BMW

Engine running lean, bank 2 (cylinders 4-6 on a straight six). With P0171 it points to a leak affecting the whole engine.

Usual causes: split crankcase ventilation valve membrane; intake or vacuum leak; weak fuel pressure; air mass meter fault

Holden

Engine running lean, bank 2. Seen on 2006-2013 Commodore Alloytec V6; with P0171 it points to something affecting both banks, like an air leak or the MAF.

Usual causes: vacuum or PCV hose leak; intake manifold gasket leak; dirty or faulty MAF sensor; weak fuel pump or blocked filter

Jeep

Fuel system too lean, bank 2.

Usual causes: vacuum leak; intake manifold gasket; weak fuel delivery

Mercedes-Benz

Engine running lean, bank 2 (V6/V8). Usually a MAF or vacuum leak problem.

Usual causes: dirty or faulty MAF sensor; vacuum or PCV leak; clogged fuel injectors

Nissan

Engine running lean on bank 2 (V6). On VQ35 often with P0171.

Usual causes: collapsed or torn PCV/breather hose at rear of intake; dirty MAF sensor; hardened intake manifold / plenum gaskets; cracked intake boot after MAF

What the repair usually costs

MAF (mass air flow) sensor replaceNZ$170–NZ$660 · A$160–A$600
High-pressure fuel pump (GDI petrol or common-rail diesel)NZ$1,140–NZ$4,280 · A$1,060–A$3,800
Engine air filter replacementNZ$40–NZ$130 · A$30–A$120

Not sure what P0174 means on your car? Ask Credov.

Before you clear it

Write the code down or photograph the scanner first. A code that comes straight back after clearing points to a fault that is still there. A car whose codes were cleared just before you arrived may be hiding one: the scanner's readiness monitors show "not ready" for a while after codes are cleared.

Researched by Credov from manufacturer and workshop sources. A fault code points to where a fault may be; a workshop confirms it with a diagnosis. Browse all fault codes.