P2273: O2 Sensor Signal Biased/Stuck Rich Bank 2 Sensor 2

What Does The P2273 Code Mean?

This P2273 diagnostic trouble code (DTC) refers to the post-catalytic converter O2 (oxygen) sensor on bank #2, sensor #2. This post-cat sensor is used for monitoring the efficiency of the catalytic converter. The converter’s job is to reduce emissions out the tailpipe. When the signal from the O2 sensor is detected by the PCM as being stuck Rich or biased Rich, this DTC is set.

The P2273 DTC refers to downstream sensor (after the catalytic converter), sensor #2 on bank #2. Bank #2 is the side of the engine that does not contain the #1 cylinder. There may be a third sensor downstream, if that is the problem, a P2277 is set.

This code is basically telling you that the signal put out by the particular oxygen sensor is stuck rich (meaning too little air in the exhaust). It is somewhat common to see both the P2271 and P2273 codes set at the same time, depending on the vehicle and root cause of the problem.

What Are The Symptoms Of The P2273 Code?

Most likely you will not notice any drivability issues since this is not sensor #1. You will notice Malfunction Indicator Lamp (MIL) illumination. In some cases however, the engine may run rough.

What Are The Potential Causes Of The P2273 Code?

The causes for this DTC may include:

• Contaminated or failed HO2S2 (Sensor 2)
• HO2S2 wiring/circuit problem
• Fuel pressure incorrect
• Faulty fuel injector
• Engine coolant leak
• Faulty purge solenoid valve
• PCM has failed

How Can You Fix The P2273 Code?

Visually inspect the wiring and connectors for corrosion, rubbed / chafed / bent wires, wiring pins bent/loose, burnt appearance, and/or crossed wires. Repair or replace as required.

Check for exhaust leaks or other problems, repair as necessary.

Using a digital volt ohm meter (DVOM) set to ohms, check harness connectors for resistance. Compare to manufacturer specifications. Replace or repair as required.

If you have access to an advanced scan tool, use it to monitor the sensor readings as viewed by the PCM (engine running, at normal operating temperature in closed loop mode). The rear heated oxygen sensor (HO2S) normally sees a fluctuating voltage between 0 & 1 volt, for this DTC you’ll likely see the voltage “stuck” at 1V. Revving the engine should cause the sensor’s voltage to change (react).

The most common fixes for this DTC seem to be either an exhaust air leak, a wiring problem with the sensor/wiring, or the sensor itself. If you replace the O2 sensor, buy an OEM one (manufacturer brand) for best results.

If you remove the HO2S oxygen sensor, inspect it for contamination from fuel, engine oil, and coolant.

Other troubleshooting ideas: Use a fuel pressure tester, check the fuel pressure at the Schrader valve on the fuel rail. Compare to manufacturers specification. Inspect the purge solenoid valve. Inspect fuel injectors. Inspect coolant passages for leaks.

Recommended Parts

Below are some recommended auto parts to help you address the trouble code affecting your vehicle and get it running smoothly again:

>>> O2 Sensor
>>> 8Pcs Fuel Injector 2 Holes
>>> Purge Solenoid Valve
>>> ECU
>>> KAIWEETS Digital Multimeter

Note: During the purchasing process, please check carefully whether the part you want to buy fits your car!

Reference Sources

Diagnostic Trouble Code (DTC) Charts and Descriptions – Page 4-145.