OBD2 codes.
A code identifies a signal or system that needs to be checked, not a part you should replace.
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P0175Mixture too rich (bank 2)Urgency medium
System Too Rich (Bank 2)
The engine is getting more fuel or less air than it should: this is called a “rich mixture”. The engine computer tries to make up for it by taking fuel away and, when it reaches its limit, it stores this code. “Bank 2” is the side of the engine opposite cylinder 1: it only exists on V engines or engines with two cylinder banks, not on inline four-cylinder engines.
What the car has detected
Bank 2 fuel trim (the amount the engine computer adds to or takes away from the planned fuel quantity) has reached the limit of what it can take away, while the oxygen sensor in the exhaust still reads a rich mixture.
It is not usually dangerous in the short term, but it uses more fuel, fouls the spark plugs and the extra fuel can overheat and damage the catalytic converter. Get it sorted soon.
Symptoms
- Engine warning light on
- Higher fuel consumption
- Black smoke from the exhaust
- Strong fuel smell
- Rough idle
- Sooty spark plugs
Possible causes
- Leaking or stuck-open injector
- Mass air flow sensor (the sensor that measures incoming air) dirty or reading wrong
- Fuel pressure too high, for example from a stuck regulator
- Clogged air filter restricting airflow
- Purge valve (the one that collects fuel tank vapours) stuck open
- Oil diluted with fuel or overfilled, or a faulty front oxygen sensor
Checks for the garage
- Read the freeze frame data and fuel trims: a long-term value well below zero confirms the rich condition
- Check the air filter, the intake and the mass air flow sensor
- Check the oil level and whether it smells of fuel
- Measure fuel pressure and compare it with the manufacturer's figure
- Run an injector balance test to find one that leaks
- Check that the purge valve closes properly
Next step
Check the air filter and the oil level (and that the oil doesn't smell of fuel), and ask for the mass air flow sensor, fuel pressure and injectors to be checked.
Go to a garage if the air filter is fine and the code comes back, if there is black smoke or a fuel smell: pressure and injector tests need equipment, and a leaking injector can damage the catalytic converter.