P0175
System Too Rich Bank 2.
- Generic
- Powertrain
- Generic code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 1
- AreaFuel and air metering
- 75
- FaultThe specific fault in that area
What it means
P0175 means the engine control unit has found that the air-fuel mixture on bank 2 is running richer than expected. Long-term and short-term fuel trims have been pulled negative to the limit of their range, so the ECU cannot take away any more fuel to correct it. Bank 2 is the side of the engine that does not contain cylinder number one, and the layout varies by engine.
Symptoms
- Malfunction indicator lamp on
- Poor fuel economy
- Rough or unstable idle
- Black smoke or a strong fuel smell from the exhaust
- Hesitation or sluggish acceleration
- Hard starting or stalling, especially when warm
Possible causes
- Leaking or stuck-open fuel injector on bank 2 delivering too much fuellikely
- Faulty or contaminated mass airflow sensor under-reading the air entering the enginelikely
- Fuel pressure too high due to a faulty regulator or restricted return line (where fitted)possible
- Faulty or slow bank 2 upstream oxygen or air-fuel ratio sensor, or damaged wiring to itpossible
- Restricted air intake, such as a blocked air filter or collapsed intake ductpossible
- Purge valve stuck open, letting excess fuel vapour into the intake from the evaporative systempossible
- Engine oil contaminated with fuel or a faulty coolant temperature sensor causing over-fuellingrare
How to diagnose
- Read freeze frame data and note engine temperature, load, speed and fuel trim values when the code set, and check for other stored codes, especially bank 1 rich codes or misfire codes.
- Inspect the air filter, intake ducting and air filter housing for blockages or damage, and look for fuel smell or wet spark plugs.
- Inspect the wiring and connectors for the bank 2 upstream sensor and the mass airflow sensor for damage, corrosion or contamination.
- Compare live short-term and long-term fuel trims on both banks at idle and at a steady 2,500 rpm to see whether the fault is bank 2 only or both banks.
- Check the mass airflow sensor reading against expected values at idle and check the sensor element for contamination.
- Check fuel pressure against the manufacturer's specification and check for fuel in the vacuum line of the regulator if one is fitted.
- Test the purge valve for sticking open by checking whether it holds vacuum when it is not commanded.
- Check the bank 2 injectors for leakage or poor spray pattern, and check the oil for a fuel smell or a rising level.
How to fix
- Replace or clean the leaking or faulty fuel injector as the testing indicates, and change the engine oil if it is fuel-diluted.
- Clean or replace the mass airflow sensor if it is reading low or is contaminated.
- Replace the fuel pressure regulator or repair the fuel return restriction if pressure is above specification.
- Replace the bank 2 upstream oxygen or air-fuel ratio sensor, or repair the damaged wiring or connector.
- Replace the air filter and repair any intake restriction.
- Replace the purge valve if it is stuck open.
Can I keep driving?
Medium severity
The car can usually be driven for a short time, but it should be checked soon. Running rich for long wastes fuel, can foul spark plugs, dilute the engine oil and may damage the catalytic converter.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.