OBD-II Generic Error Code P2240: How to Fix It

Q: What does P2240 mean on my car?

P2240 means the engine control module (ECM) has detected a fault in the pumping current circuit of the heated oxygen sensor (HO2S) on Bank 2, Sensor 1 — the upstream oxygen sensor on the engine bank that does not contain cylinder number 1. This circuit controls the small electrical current used to measure oxygen concentration in the exhaust stream.

Q: Can I drive with a P2240 code?

You can drive short distances, but it is not recommended for extended periods. The faulty oxygen sensor causes the ECM to run on default fuel maps, which can lead to rich or lean running conditions, reduced fuel economy, potential catalytic converter damage over time, and a failed emissions test. Fix the issue as soon as possible.

Q: How much does it cost to fix a P2240 code?

If the repair is just a replacement oxygen sensor, expect to pay $50–$150 for a quality aftermarket sensor or $100–$300 for an OEM sensor, plus $75–$150 in labor at a shop. If the problem is a wiring harness repair, costs may be $100–$400 depending on the extent of damage. ECM replacement or reprogramming is significantly more expensive, ranging from $500 to $1,500 or more.

Q: Which oxygen sensor is Bank 2 Sensor 1?

Bank 2 is the side of the engine that does NOT contain cylinder number 1. Sensor 1 means it is the upstream (pre-catalytic converter) sensor — the one closest to the engine, typically threaded directly into the exhaust manifold or the front section of the exhaust pipe. Consult your vehicle's service manual to confirm which bank is which, as it varies by engine configuration.

Q: Will a bad oxygen sensor cause a failed emissions test?

Yes. A faulty oxygen sensor almost always causes your vehicle's OBD2 readiness monitors to show as 'Not Ready' or 'Incomplete,' which results in an automatic emissions test failure in most states, regardless of actual tailpipe emissions. You must repair the fault and complete a full drive cycle to set the monitors before testing.

Abstract

Error code P2240 indicates a fault in the heated oxygen sensor (HO2S) pumping current circuit for Bank 2, Sensor 1 — the upstream oxygen sensor on the side of the engine that does NOT contain cylinder number one. This sensor is critical for the engine control module (ECM) to accurately measure exhaust oxygen levels and maintain proper air-fuel ratios. When this circuit malfunctions, your vehicle may run rich or lean, reduce fuel economy, and fail emissions testing.