O2 Sensor Signal Biased/Stuck Rich Bank 2 Sensor 2
The Powertrain Control Module (PCM) monitors the downstream oxygen sensor to evaluate catalytic converter efficiency. Code P2273 is set when the PCM detects that the Bank 2 Sensor 2 signal is continuously stuck in a rich condition (high voltage) and fails to fluctuate normally.
This issue will not immediately strand you, but it will cause you to fail an emissions test. It should be diagnosed soon to prevent potential long-term catalytic converter damage if an actual rich condition exists.
Common symptoms
- Illuminated Check Engine Light
- Decreased fuel efficiency
- Strong fuel odor from the exhaust
- Failed emissions test
- Slightly rough idle or engine performance issues
Likely causes
- Faulty Bank 2 Sensor 2 (downstream oxygen sensor)
- Short to voltage in the O2 sensor signal circuit wiring
- Corroded or damaged O2 sensor connector
- Actual engine rich condition (e.g., leaking fuel injector or high fuel pressure)
- Faulty Powertrain Control Module (PCM)
What to check before replacing parts
Connect a scan tool and monitor the Bank 2 Sensor 2 voltage.
Look for: The voltage should fluctuate slightly around 0.45V to 0.8V; if it is stuck above 0.8V constantly, the sensor is biased rich.
Visually inspect the wiring and connector for Bank 2 Sensor 2.
Look for: Look for melted wires on the exhaust, chafing, or water intrusion in the connector that could cause a short to voltage.
Induce a temporary lean condition by creating a small vacuum leak.
Look for: Observe the scan tool; if the B2S2 voltage drops toward 0.1V, the sensor is capable of reading lean and the engine is actually running rich.
Check the short and long-term fuel trims for Bank 2.
Look for: If the fuel trims are highly negative (pulling fuel), it confirms an actual rich condition rather than just a faulty sensor.
Test the O2 sensor signal wire with a digital multimeter.
Look for: Disconnect the sensor and check for voltage on the signal wire from the PCM; it should be a steady bias voltage (usually 0.45V), not a full 5V or 12V short.
This page explains the generic P2273 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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