O2 Sensor Signal Stuck Rich (Bank 2 Sensor 2)

What it means

This code appears on engines with two banks. The engine computer found that the Bank 2 downstream sensor signal stayed high (showing rich) even during fuel cut-off on deceleration. This usually means a contaminated sensor or a shorted circuit, and sometimes a real rich mixture on that bank.

Related codes: P2272P2271P0158P0175

Symptoms4

• Check engine light on, often with no other symptoms.
• Higher fuel consumption if the mixture is really rich.
• Occasional fuel or sulfur smell from the exhaust.
• Failed emissions test.

Possible causes5

• Bank 2 downstream sensor contaminated by oil, coolant or silicone.
• Failed or aged Bank 2 downstream oxygen sensor.
• Signal wire shorted to a voltage source.
• A real rich mixture on Bank 2 from a leaking injector on that bank.
• Engine computer fault (rare).

How to diagnose5

1. Fix any rich mixture codes such as P0175 first.
2. Locate Bank 2 and its downstream sensor in the service information.
3. Watch the sensor voltage while coasting off the throttle; it should drop clearly. Compare it with the Bank 1 downstream sensor.
4. Compare fuel trims between banks; large negative values on Bank 2 alone point to a real rich condition there.
5. Check the signal wire for a short to voltage and inspect the sensor tip for contamination.

How to fix5

1. Repair the wire shorted to voltage or the damaged connector.
2. Fix the cause of a rich mixture on Bank 2, such as a leaking injector.
3. Fix the cause of oil burning or coolant loss if present.
4. Replace the Bank 2 downstream oxygen sensor.
5. Clear the codes and drive until the sensor self-test completes.

The cost is low for a wire or connector repair, reaches the upper end when the sensor is replaced, and may be more if another cause such as a leaking injector is found.

Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026

Frequently asked questions