OBD-II Generic Error Code P2255: How to Fix It

Q: What does HO2S negative current control low B2S1 mean?

It means the Engine Control Module (ECM) detected that the electrical signal controlling the negative current of the Bank 2 Sensor 1 heated oxygen sensor is lower than the expected range. This sensor sits upstream of the catalytic converter on the side of the engine opposite cylinder #1. The fault is typically caused by a bad sensor, damaged wiring, poor ground connection, or rarely an ECM fault.

Q: Can I drive my car with a P2255 code?

You can typically drive short distances with P2255 active, but it is not recommended for extended driving. A faulty upstream oxygen sensor causes the ECM to miscalculate the air-fuel mixture, which can lead to poor fuel economy, increased emissions, and over time, damage to the catalytic converter — a very expensive repair. Get the code diagnosed and fixed as soon as reasonably possible.

Q: How do I know which side is Bank 2 on my engine?

Bank 2 is the side of the engine that does NOT contain cylinder number 1. For most inline 4-cylinder engines, there is only one bank so Bank 2 does not apply. For V6 and V8 engines, Bank 1 contains cylinder #1 and Bank 2 is the opposite side. Consult your vehicle's service manual or a reliable online firing order diagram for your specific engine to confirm which physical side is Bank 2.

Q: Will P2255 cause a failed emissions test?

Yes. A P2255 code will illuminate the Check Engine Light, and in most states and regions, any active Check Engine Light is an automatic failure on an emissions/smog test. Even if the light is cleared shortly before the test, emissions test computers check readiness monitors — if the oxygen sensor monitor has not completed its drive cycle, the vehicle will still fail. Fix the underlying problem first, then run the required drive cycle to complete all readiness monitors before retesting.

Q: How much does it cost to fix a P2255 code?

If the fix is a straightforward oxygen sensor replacement, expect to pay roughly $50–$150 for the part (depending on your vehicle and whether you choose OEM or aftermarket) plus $50–$150 in labor if done by a shop, for a total of $100–$300. Wiring repairs can add $100–$300 depending on severity. If the ECM is determined to be faulty, costs can rise to $500–$1,500 or more including programming. DIY sensor replacement typically costs only the price of the part plus any tools needed.

Abstract

Error code P2255 indicates a fault in the negative current control circuit of the upstream oxygen sensor (Heated Oxygen Sensor, Bank 2 Sensor 1). This sensor monitors exhaust gases before the catalytic converter on the side of the engine that does not contain cylinder #1, and the ECM has detected that the sensor's current control signal is reading abnormally low. Left unaddressed, this fault can cause poor fuel economy, failed emissions tests, and potential catalytic converter damage.