OBD-II Generic Error Code P2347: How to Fix It

Q: Can I still drive my car with a P2347 code?

You can drive short distances with caution if there is no audible knocking and the vehicle is running normally, but it is not recommended for extended driving. The ECM will typically retard ignition timing to reduce knock, which hurts performance and fuel economy. If you hear actual knocking or pinging sounds, stop driving immediately — continued use can cause serious internal engine damage.

Q: What does 'above knock threshold' mean in P2347?

The ECM uses knock sensors to listen for abnormal vibrations caused by uncontrolled combustion (detonation) in each cylinder. Each cylinder has a normal vibration range. 'Above knock threshold' means the sensor detected vibration intensity in Cylinder 12 that exceeded the acceptable limit, indicating that detonation or pre-ignition is occurring in that specific cylinder.

Q: How much does it cost to fix a P2347 code?

Cost depends on the root cause. A spark plug replacement is the cheapest fix at roughly $10–$50 for parts, plus labor if a shop does it. A knock sensor replacement typically costs $50–$150 for the sensor plus $100–$300 in labor depending on accessibility. If the problem is related to the ignition system, fuel injectors, or internal engine damage, costs can range from a few hundred to several thousand dollars. Start with the simplest fixes first.

Q: Can bad fuel cause a P2347 code?

Yes. Low-octane fuel is one of the most common triggers for engine knock codes. If the octane rating of the fuel is too low for your engine's compression ratio, the air-fuel mixture can self-ignite before the spark plug fires, causing detonation. Always use the minimum octane fuel recommended by your vehicle manufacturer, which is often printed on the fuel cap or in the owner's manual.

Q: Is P2347 the same as a knock sensor failure code?

Not exactly. P2347 specifically means that actual knock was detected above the threshold in Cylinder 12 — it is a knock event code. A knock sensor failure code (such as P0325 or P0332) means the sensor itself is not functioning properly. However, a faulty knock sensor can generate false P2347 codes, so both possibilities should be investigated during diagnosis.

Abstract

OBD-II error code P2347 indicates that the engine control module (ECM) has detected knocking or detonation in Cylinder 12 that exceeds the acceptable threshold. Engine knock happens when the air-fuel mixture ignites unevenly or prematurely, causing a characteristic pinging sound and potential engine damage if left unaddressed. This code is most common in large-displacement V12 engines and should be diagnosed promptly to protect your engine's long-term health.