P2270 – O2 Sensor Signal Biased or Stuck Lean B1S2

By Benjamin Jerew (Contact Me)
Last Updated 2017-03-15
ASE Master Tech

Trouble CodeFault LocationProbable Cause
P2270 Heated oxygen sensor (H028) 2, bank 1 - signal stuck lean Wiring, H025, fuel pressure, injectors, intake leak

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What Does Code P2270 Mean?

The catalytic converter is an emissions-control device. Once heated, at least 600 °F, the catalytic converter oxidizes exhaust gases into safer compounds. Most vehicles use a three-way catalytic converter (TWC), which are able to catalyze nitrogen oxides (NOx), carbon monoxide (CO), and unburnt hydrocarbons (HC). Unburned hydrocarbons (fuel) and oxygen combine, producing carbon dioxide, and nitrogen-oxides recombine, producing inert nitrogen and oxygen, for example.

A typical three-way catalytic converter.
A typical three-way catalytic converter.

The ECM (engine control module) monitors catalyst function by measuring oxygen levels in the exhaust after the catalytic converter. Ford even calls the post-cat heated oxygen sensor (HO2S) the Catalyst Monitor Sensor. A normally-functioning TWC will effect a change in oxygen content downstream as it chemically combines various exhaust components, resulting in a slowly variable HO2S reading downstream, slowly cycling between 0 V and 1 V. The ECM regularly tests TWC function by boosting fuel at a predetermined interval. If the HO2S does not respond with voltage over a certain threshold, indicating lower oxygen content, the ECM determines this to be a fault, sets a diagnostic trouble code (DTC) and illuminates the malfunction indicator lamp (MIL). DTC P2270 is defined as “O2 Sensor Signal Biased or Stuck Lean B1S2.”

What are the common causes of code P2270?

Depending on year, make, and model, DTC P2270 may have number of causes. Here are some of the most common.

  • Ford TSB – There is at least one Technical Service Bulletin that covers this DTC, requiring the replacement of the HO2S. There is an updated part number for some 2010-2012 Ford 4.6L, 5.4L, 6.2L, and 6.8L engines.
  • Exhaust leaks, contaminated HO2S, and loose HO2S are the most common failures notes.
  • Rarely, incorrect fuel pressure, leaking fuel injectors, or faulty EVAP purge control valves may cause this problem.

Images

Oxygen vs Voltage by Clamothe via Wikimedia

Catalytic Converter by Stahlkocher via Wikimedia

What are the symptoms of code P2270?

You will probably not notice any drivability symptoms, though your fuel economy may suffer if the failure mode puts the engine in open-loop mode.

How do you troubleshoot code P2270?

Though this DTC refers to an oxygen sensor, do not simply replace it as a matter of course. The sensor may be at fault, but do not condemn it unless you have done the rest of the tests. If there are multiple DTCs, including history codes, address those DTCs first, reset the ECM, and see if DTC P2270 comes back.

The HO2S reacts to the difference in oxygen content between the atmosphere and exhaust stream.
The HO2S reacts to the difference in oxygen content between the atmosphere and exhaust stream.
  • Exhaust Check
    • Check that there are no exhaust leaks between the engine and the HO2S. Repair as necessary.
    • Check that the HO2S is installed properly and undamaged. Adjust or replace as needed.
  • Sensor Check –
    • Check that the connector is free of corrosion or water entry. Repair as needed and ensure connector is fully seated.
    • Remove sensor and check for contamination, such as from oil or coolant. Repair as needed and recheck the system.

Codes Related to P2270

P2195 O2 Sensor Signal Biased/Stuck Lean Bank 1 Sensor 1

P2196 O2 Sensor Signal Biased/Stuck Rich Bank 1 Sensor 1

P2197 O2 Sensor Signal Biased/Stuck Lean Bank 2 Sensor 1

P2198 O2 Sensor Signal Biased/Stuck Rich Bank 2 Sensor 1

P2271 O2 Sensor Signal Biased/Stuck Rich Bank 1 Sensor 2

P2272 O2 Sensor Signal Biased/Stuck Lean Bank 2 Sensor 2

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

P2274 O2 Sensor Signal Biased/Stuck Lean Bank 1 Sensor 3

P2275 O2 Sensor Signal Biased/Stuck Rich Bank 1 Sensor 3

P2276 O2 Sensor Signal Biased/Stuck Lean Bank 2 Sensor 3

P2277 O2 Sensor Signal Biased/Stuck Rich Bank 2 Sensor 3

BAT Team Discussions for P2270

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    2000 ford taurus 3.0 dura tech 24 valve 90,000 miles. Yeah Im in a road salt area. I had the codes ran at advanced and this is what came back: 1. P0136 O2 sensor ciruit bank 1 sensor 2 (the guy at advanced said this is the upstream sensor?) (P2270, P2271) 2. P1131 The code tester at advanced did...