P0172 and P0175: system too rich
The engine computer has taken away as much fuel as it can and the mixture is still rich. P0172 is bank 1, P0175 bank 2.
SeverityModerateUsually not urgent today, but it can get worse if left.
Can you keep driving?Drive gently, check it soonWhat does P0172 mean?
Fuel trim works in both directions. A rich code means the long-term correction sits at the bottom of its range: more fuel is reaching the cylinders than the measured air needs. Black smoke, a smell of fuel and higher consumption often come with it.
What causes P0172?
- A leaking or sticking injector
- Fuel pressure that is too high, often from a faulty pressure regulator
- A mass air flow sensor that over-reads, or a blocked air filter
- A faulty coolant temperature sensor telling the computer the engine is cold
- Fuel in the engine oil, or a saturated charcoal canister feeding vapour into the intake
What to check first for P0172
- Read the coolant temperature on a scan tool: it should match a warm engine
- Check the air filter
- Have the fuel pressure and the injectors' leak-down tested
- Smell the oil dipstick for fuel
Can you drive with P0172?
The car can usually be driven to a workshop. Do not ignore it for long: a rich mixture fouls the spark plugs, overheats and clogs the catalytic converter and thins the engine oil.
Since May 2018 an engine warning light that stays on is a major defect at the MOT, so the car fails until the fault is fixed.
Codes on this page
- P0172System Too RichBank 1
- P0175System Too RichBank 2
Related codes
Checked on · Rafael Soares
These are the generic meanings every manufacturer shares. Each brand adds its own detail, so your car's handbook, its service information and a qualified mechanic have the last word. OdoKeep has no connection with any manufacturer, and the app does not read codes from the car.
