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P2273 — O2 Sensor Signal Biasedstuck Rich Bank 2 Sensor 2

Manufacturer-specificPowertrain (engine & transmission)

OBD-II code P2273 indicates that the downstream oxygen sensor (Bank 2, Sensor 2) is reporting a signal that is biased or stuck rich. This means the sensor voltage is consistently high, suggesting a rich air-fuel mixture or a sensor malfunction. The code is set when the powertrain control module (PCM) detects that the sensor's signal remains above a calibrated threshold for too long, indicating it is not switching as expected.

Symptoms

What causes it — most likely first

1. Faulty Bank 2 Sensor 2 oxygen sensor

The sensor itself may be contaminated, aged, or internally shorted, causing it to output a constant high voltage signal.

2. Wiring or connector issues at Bank 2 Sensor 2

Damaged, corroded, or shorted wiring or a poor connection at the sensor harness can cause a false rich signal to be sent to the PCM.

3. Exhaust leak near the downstream sensor

An exhaust leak upstream of or near the Bank 2 Sensor 2 location can introduce fresh air, causing the sensor to read lean, but in some cases the PCM may misinterpret the signal as biased rich if the leak is intermittent or affects sensor heating.

4. Rich running condition (e.g., leaking fuel injector, high fuel pressure)

A genuine rich air-fuel mixture on Bank 2, caused by a leaking injector, excessive fuel pressure, or a faulty upstream O2 sensor, can saturate the downstream sensor and keep its voltage high.

5. Contaminated or damaged catalytic converter

A failing catalytic converter on Bank 2 may cause abnormal downstream O2 sensor readings, though this is less common for a stuck rich signal unless the converter is severely contaminated.

6. PCM software or hardware malfunction

Rarely, the powertrain control module may have an internal fault causing it to misinterpret sensor signals, but this should only be considered after all other causes are ruled out.

How it's diagnosed

  1. Retrieve all codes and freeze frame data. Check for any additional codes that may indicate a rich condition or sensor circuit issues.
  2. Visually inspect the Bank 2 Sensor 2 wiring and connector for damage, corrosion, or loose connections. Repair as needed.
  3. Check for exhaust leaks before the sensor. Listen for hissing or tapping sounds, and inspect the exhaust system for cracks or loose connections.
  4. Use a scan tool to monitor the Bank 2 Sensor 2 voltage in real time. A normal downstream sensor should switch slowly or remain steady around 0.45V after the engine is warm. If the voltage is stuck high (above 0.8V), disconnect the sensor and check if the voltage drops to a reference bias (typically around 0.45V). If it does, the sensor is likely shorted internally. If it stays high, the wiring or PCM may be at fault.
  5. Check for a rich running condition by inspecting fuel trims, upstream O2 sensor data, and performing a fuel pressure test. Look for leaking injectors or a faulty fuel pressure regulator.
  6. If no other issues are found, perform a voltage drop test on the sensor signal and ground circuits to rule out wiring problems before considering PCM replacement.

Code facts & related codes

SystemPowertrain (engine & transmission)
StandardizationManufacturer-specific (P1/B1/C1/U1)
Related codesP2270 — O2 Sensor Signal Biasedstuck Lean BankP2271 — O2 Sensor Signal Biasedstuck Rich BankP2272 — O2 Sensor Signal Biasedstuck Lean BankP2274 — O2 Sensor Signal Biasedstuck Lean BankP2275 — O2 Sensor Signal Biasedstuck Rich BankP2276 — O2 Sensor Signal Biasedstuck Lean Bank

Frequently asked

Can I just replace the O2 sensor to fix this code?

Often yes, because a failed sensor is the most common cause. However, it's important to first check for exhaust leaks, wiring damage, or a genuine rich condition that could damage a new sensor. Replacing the sensor without diagnosing the root cause may lead to the code returning.

Is this code caused by a bad catalytic converter?

It's unlikely. A failing catalytic converter typically causes a P0420 or P0430 code. P2273 specifically indicates a stuck rich signal from the downstream sensor, which is more often a sensor or wiring issue, or an actual rich condition.

Could the PCM be the problem?

PCM failure is extremely rare for this code. The PCM is often misdiagnosed. Only consider PCM replacement after thoroughly testing the sensor, wiring, and fuel system, and confirming that the PCM is not properly processing the sensor signal.

Can I drive with a P2273 code?

Driving for a short period is usually safe, but a rich condition can damage the catalytic converter and reduce fuel economy. It's best to diagnose and repair the issue promptly.