System Too Rich Bank 2
The Engine Control Module (ECM) has detected that the air-fuel mixture for Bank 2 (the side of the engine opposite cylinder 1) is too rich, meaning there is too much fuel or not enough air. It sets this code when the short-term and long-term fuel trims exceed their negative limits in an attempt to lean out the mixture.
While the vehicle can usually still be driven, running too rich for an extended period can damage the catalytic converter and foul the spark plugs. It should be diagnosed and repaired soon to prevent further component damage and poor fuel economy.
Common symptoms
- Illuminated Check Engine Light
- Decreased fuel economy
- Rough idle or engine hesitation
- Black smoke from the exhaust
- Strong smell of unburned fuel from the exhaust
Likely causes
- Dirty or faulty Mass Air Flow (MAF) sensor
- Leaking or stuck open fuel injector on Bank 2
- Faulty oxygen (O2) sensor or air-fuel ratio sensor on Bank 2
- Excessive fuel pressure (faulty fuel pressure regulator)
- Restricted air intake or clogged engine air filter
- Exhaust leak before the Bank 2 oxygen sensor
What to check before replacing parts
Check the engine air filter and intake system
Look for: Look for a heavily clogged air filter or blockages in the intake tract that could restrict airflow and cause a rich condition.
Clean and test the Mass Air Flow (MAF) sensor
Look for: Look for a dirty sensor wire. Use a scan tool to verify MAF g/s readings match engine displacement at idle and increase smoothly with RPM.
Monitor live fuel trim data using a scan tool
Look for: Look for Bank 2 long-term fuel trims (LTFT) that are consistently negative (e.g., -15% or worse), confirming the rich condition.
Test fuel pressure with a mechanical gauge
Look for: Look for fuel pressure that exceeds the manufacturer's specification, which could indicate a failing fuel pressure regulator or restricted return line.
Inspect Bank 2 spark plugs and perform an injector leak-down test
Look for: Look for soot-fouled spark plugs on Bank 2 or a rapid drop in fuel pressure after engine shutdown, indicating a leaking fuel injector.
This page explains the generic P0175 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
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