P0175: System Too Rich (Bank 2)

What it means

Same condition as P0172 but on bank 2. When paired with P0172, suspect shared causes (fuel pressure, blocked air filter); when alone, suspect a bank-specific injector or oxygen sensor.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

The ECU uses bank 2 oxygen-sensor feedback to adjust fuel delivery for that side of the engine. P0175 sets when it detects that bank 2 is persistently richer than its target and fuel correction cannot bring the mixture back within limits.

Common causes

Most likely first.

1. Fuel pressure regulator stuck closed
2. Leaking fuel injector on bank 2

Symptoms

• Check engine light on
• Increased fuel consumption
• Black smoke from exhaust on acceleration
• Smell of unburned fuel, fouled spark plugs

How to diagnose it

1. Check freeze-frame data and compare bank 2 fuel trims and oxygen-sensor readings with bank 1 to determine whether the rich condition is limited to bank 2.
2. Inspect the air filter and intake tract for restrictions that could affect the whole engine, especially if other banks also show rich trims.
3. Look for fuel smell, black exhaust deposits, or a wet or fouled spark plug on a bank 2 cylinder that could point to a leaking injector.
4. Check fuel pressure and regulator operation against the manufacturer's specification, particularly if both banks are rich.
5. Test the bank 2 injectors and oxygen sensor using scan data and appropriate circuit checks before replacing parts.

Common fixes

• Replace a restricted air filter if inspection confirms airflow is limited.
• Repair or replace a fuel pressure regulator that fails testing.
• Repair a leaking bank 2 injector after confirming which injector is responsible.
• Replace the bank 2 oxygen sensor if its response is faulty and other causes are ruled out.

Can I keep driving?

Avoid driving if there is strong fuel odor, visible black smoke, severe misfiring, or a flashing check-engine light; arrange prompt repair. Excess fuel can foul spark plugs and overheat or damage the catalytic converter.