P2270 Code: O2 Sensor Signal Stuck Lean Bank 1 Sensor 2

Read Time: 2 mins

p2270 code displaying on an OBD-2 diagnostic tool with a gradient background made up of three colors—blue, green and beige

Table of Contents

What does the P2270 code mean?

The P2270 code means the oxygen sensor signal is stuck in lean bank 1 sensor 2. The car’s computer can’t understand this information and sets a P2270 code. It’s essential to understand what that means because there are other causes for this error message, and a mechanic will need to know which one you’re dealing with before they can fix it.

What is the definition of P2270?

P2270 is a generic OBD-II code that means the signal from the oxygen sensor is stuck lean. The oxygen sensor is located on the exhaust manifold and monitors the oxygen content in the exhaust pipe. If your car detects too much oxygen in one bank, it will set this code.

What are the common causes of the P2270 code?

The following is a list of the most common causes of this code:

  • O2 sensor failure
  • O2 sensor harness or connector failure
  • O2 sensor circuit low voltage (less than .6 volts) or high voltage (greater than 4.6 volts)
  • Exhaust leaks in front of the catalytic converter can cause an incorrect reading from the downstream O2 sensors on both sides of the engine. This is usually due to a cracked manifold, head gasket leaks around exhaust ports, or cracked heads with holes in them, allowing air into your exhaust system and causing inaccurate readings from your upstream O2 sensors.

What are the symptoms of the P2270 code?

  • Check the engine light on
  • Poor fuel economy
  • Rough idle
  • Engine misfire (misfiring or rough running) or no start condition can be caused by a failed ignition coil pack or spark plug wires that are frayed and corroded

How does a mechanic diagnose a P2270 code?

To diagnose a P2270 code, a mechanic will usually do the following:

Perform a diagnostic test drive: The mechanic will observe your car’s performance under different driving conditions. Any noticeable differences in performance between one bank of cylinders and another could indicate something wrong with one of those banks’ sensors or spark plugs.

Check the O2 sensor(s): An oxygen sensor monitors the amount of oxygen in each cylinder; if one isn’t working correctly, it could cause your car to run poorly because it thinks there is too much fuel being injected into that cylinder when there isn’t enough oxygen present for combustion to occur properly (lean condition). This would result in an exhaust leak at idle speeds due to insufficient combustion pressure inside each chamber, which would explain why small amounts of black smoke were coming out from underneath my tailpipe during diagnosis.


The P2270 code is a generic O2 sensor diagnostic code that applies to many vehicles. The best way to diagnose this code is by using an OBD-II scanner or having your car inspected by a professional mechanic who will check for any leaks in the exhaust system and any bad connections between sensors and wiring harnesses.