P2270 O2 Sensor Signal Bias / Stuck Lean Bank 1 Sensor 2
OBD2 Error Codes

P2270 O2 Sensor Signal Bias / Stuck Lean Bank 1 Sensor 2

P2270 O2 Sensor Signal Bias / Stuck Lean Bank 1 Sensor 2

OBD-II DTC Datasheet

O2 Sensor Signal Bias / Stuck Lean Bank 1 Sensor 2

What does this mean?

This is a generic transmission code which means it applies to all OBD-II vehicles from 1996 onwards. Car brands may include, but are not limited to, Chevy, Subaru, GMC, Ford, Mini, VW, Mazda, etc. However, specific troubleshooting steps may differ from vehicle to vehicle.

This Diagnostic Trouble Code (DTC) P2270 applies to the Post-Catalytic Converter O2 (oxygen) sensor on block # 1, sensor # 2. This post-cat sensor is used to monitor the efficiency of the catalytic converter. The converter's job is to reduce exhaust emissions. This DTC sets when the PCM detects the signal from the O2 sensor as stuck lean or misaligned lean.

DTC P2270 refers to the downstream sensor (after the catalytic converter), sensor #2 on bank #1. Bank #1 is the side of the engine that contains cylinder #1. There may be a third sensor on the output, if this is a problem, P2274 is set.

This code basically tells you that the signal given by a specific oyxgen sensor is stuck in a lean mixture (which means there is too much air in the exhaust).

Note. Some manufacturers, such as Ford, may refer to this as the catalyst monitor sensor, the same thing but in a different way. This DTC is very similar to P2195. If you have multiple DTCs, fix them in the order they appear.

Typical oxygen sensor O2: P2270 O2 Sensor Signal Bias / Stuck Lean Bank 1 Sensor 2


Chances are you won't notice any handling issues as this is not sensor # 1. You will notice that the Malfunction Indicator Light (MIL) comes on. However, in some cases, the engine may run intermittently.

Possible reasons

Reasons for this DTC may include:

  • Exhaust gas leak near O2 sensor
  • Dirty or defective HO2S2 sensor (sensor 2)
  • HO2S2 Wiring / Circuit Problem
  • Free installation of the HO2S2 sensor
  • Incorrect fuel pressure
  • Defective fuel injector
  • Leaking engine coolant
  • Defective purge solenoid valve
  • PCM out of order

Diagnostic and repair procedures

Visually inspect wiring and connectors for corrosion, scuffed / abraded / kinked wires, bent / loose wiring pins, burnt and / or crossed wires. Repair or replace as needed.

Check for exhaust leaks and repair if necessary.

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

If you have access to the advanced scan tool, use it to monitor the sensor reading as seen by the PCM (engine running at normal operating temperature in closed loop mode). The rear heated oxygen sensor (HO2S) usually sees voltage fluctuations between 0 and 1 volt, for this DTC you will probably see the voltage stuck at 0 V. Rotating the engine should cause the sensor voltage to change (react).

The most common fixes for this DTC are an exhaust air leak, a problem with the sensor / wiring wiring, or the sensor itself. If you are replacing your O2 sensor, buy an OEM (brand name) sensor for best results.

If you are removing the HO2S, check 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 with manufacturer's specification. Inspect the purge solenoid valve. Inspect the fuel injectors. Inspect the coolant passages for leaks.

Additional Notes:

There is a Ford Technical Service Bulletin (TSB) 14-0084, which applies to some 2010-2012 F-150, Navigator, Ranger, E-Series and other vehicles, which says to replace the O2 sensor when DTCs P2270 or P2272 are found ...

There is Chrysler Dodge Jeep Service Bulletin 18-011-08 which mentions this DTC related to certain 2008-2010 Compass, Patriot, Sebring, Avenger and Caliber models. If the DTC appears intermittently, check if the code and bulletin apply to you. The fix in this case is to reprogram the PCM.

There may be other TSBs that relate to other makes and models related to this DTC, contact your dealership's service department or online source to find any specific TSBs that apply to your vehicle.

P2270 code diagnostic video

Here is a video that pertains to the Ford O2 sensor circuit test. An example is a 2005 Mercury Sable with code P2270, the procedure will be the same for other makes / models. We are not affiliated with the producer of this video:

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Need more help with the P2270 code?

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