P0175: System Too Rich Bank 2
P0175 means the engine computer has detected that the air-fuel mixture on bank 2 (the side of the engine that does not hold cylinder 1) is too rich, with too much fuel for the amount of air. You can usually keep driving for a short time, but it should be fixed soon because it wastes fuel and can damage the catalytic converter later.
You can drive, but get it checked soon
The engine does not go into limp mode, so short trips are usually possible. A rich mixture raises fuel use and can damage the catalytic converter over time, and fuel can dilute the engine oil, so do not put off the repair for long.
What it means
The engine computer constantly adjusts how much fuel is injected, using the oxygen sensor in the exhaust to check the result. Short-term fuel trim reacts within fractions of a second. Long-term fuel trim is a learned base correction stored for different loads and engine speeds. Negative values mean fuel is being removed because the mixture was rich, and values around ±10 % are normal. P0175 is stored when the long-term correction has reached its lower limit and the mixture is still rich. It is the bank 2 counterpart of P0172. If P0175 appears alone, the cause is likely specific to bank 2, such as a leaking injector. If it appears together with P0172, the cause is more likely shared by both banks, such as fuel pressure, the purge valve, wrongly learned ethanol content on flex-fuel vehicles, or fuel in the oil. The code needs two trips to set the check engine light, and it does not cause limp mode.
Likely causes
- Purge valve stuck open or charcoal canister saturatedVery likely
A stuck-open purge valve lets fuel vapor from the charcoal canister flow into the engine when it should not, and GM and Ford bulletins list this as a documented cause.
- Leaking or dripping injectors on bank 2Possible
An injector that leaks adds fuel the computer did not ask for, which pushes the mixture rich on that bank; this also applies to direct injection.
- Fuel pressure too highPossible
A faulty regulator, a blocked return line, or a problem with the regulator's vacuum hose can raise pressure so each injector delivers more fuel than intended.
- Fuel in the engine oilPossible
Fuel that gets into the oil, from short trips or leaking injectors, can evaporate and enter the intake through crankcase ventilation, enriching the mixture.
What you may notice
- Check engine light on (after two drive cycles)
- Higher fuel consumption and a fuel smell
- Black smoke from the exhaust and sooty spark plugs
- Rough idle or hard starting after refueling
- Possible catalytic converter damage later if it is left unrepaired
What to check, cheapest first
- 1Read the stored codes and note whether P0172 is also present. P0175 alone points to bank 2, while both codes together point to a shared cause. · you can do it
- 2Check the engine oil level and smell the oil. A level that has risen or a strong fuel smell suggests fuel is getting into the oil. · you can do it
- 3Inspect the purge valve and its vacuum hoses for damage, and check whether the valve is stuck open. · you can do it
- 4Check the fuel pressure regulator's vacuum hose and the regulator itself for fuel or damage. · mechanic
- 5Measure fuel pressure and look at live fuel trim data on both banks to separate a bank-specific fault from a shared one. · mechanic
- 6Test the bank 2 injectors for leaking or dripping, and on flex-fuel vehicles check whether the ethanol content has been learned incorrectly. · mechanic
Related codes
Frequently asked questions
Can I drive with a P0175 code?+
Short drives are usually possible because the code does not cause limp mode. Have it repaired soon, since the rich mixture wastes fuel and can harm the catalytic converter and dilute the oil.
Can a gas cap cause P0175?+
The reference data does not list the gas cap as a cause. A stuck-open purge valve or saturated charcoal canister is the most likely cause.
Will P0175 pass an emissions test?+
Probably not. The code is emissions-relevant and turns on the check engine light, which normally means a vehicle fails until the fault is fixed.
Can I fix P0175 myself?+
Often yes, depending on the cause. Repair difficulty is medium, and the work takes roughly 0.5 to 4 hours. Checking the purge valve and hoses is a reasonable starting point, while injector and fuel pressure work may need a mechanic.
Written with the help of AI from the public OBDex definition (CC0). Each make may use the code differently. Updated: 2026-11-10