P0331
Knock Sensor 2 Circuit Range/Performance (Bank 2)P0331 is a generic OBD-II powertrain diagnostic trouble code: Knock Sensor 2 Circuit Range/Performance (Bank 2). It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0331 means
P0331 is stored when the ECM determines that the Knock Sensor 2 signal on Bank 2 is outside the expected range or does not respond appropriately during combustion events. This is a rationality fault: the sensor circuit is electrically intact, but the signal amplitude or pattern does not match what the ECM expects when knocking conditions are present or artificially induced. In other words, the sensor exists but is not performing its monitoring function correctly.
The ECM continuously compares the knock sensor output to an internal model of normal engine vibration. If actual knock events are detected acoustically but the KS2 signal fails to reflect them, or if the signal is implausibly high without a corresponding combustion event, P0331 is triggered. Consequences include the ECM defaulting to conservative ignition timing on Bank 2, reducing power and fuel economy. A loose sensor (poor mechanical coupling to the block), low fuel octane, or early bearing/piston wear generating abnormal vibration can all contribute to a rationality failure.
Common causes
Most-frequently reported root causes when P0331 is logged.
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1
Knock sensor 2 mounting bolt loose or undertorqued, reducing vibration coupling to block
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2
Failed or degraded knock sensor 2 piezoelectric element producing a weak or flat signal
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3
Wiring fault (high resistance, partial short) attenuating the sensor signal
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4
Incorrect fuel octane causing knock events that exceed the sensor's or ECM's adaptive range
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5
Actual mechanical engine knock on Bank 2 (worn bearings, carbon buildup) that the sensor cannot suppress via timing retard alone
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6
Contaminated or damaged sensor connector introducing signal noise
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7
ECM software issue or failed knock-input channel (diagnose last)
Symptoms drivers notice
How to diagnose P0331
A typical diagnostic flow when this code is present.
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1
Record all DTCs and freeze-frame data; note any related Bank 2 misfire codes that could point to a mechanical cause
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2
Inspect the knock sensor 2 connector and harness for corrosion, loose pins, or chafed wiring in the Bank 2 area
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3
Verify the sensor is torqued to specification (typically 15–25 Nm depending on manufacturer) — overtightening or undertightening both degrade the piezo response
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4
With ignition on, confirm 5 V reference at the sensor connector and a clean ground return
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5
Test knock sensor 2 resistance with a DVOM against manufacturer specs; a reading far outside range indicates a failed sensor
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6
With the engine running, tap the block near the sensor and monitor timing retard on a scan tool — the ECM should show timing pull if the sensor is functioning
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7
Verify correct fuel octane is being used; fill with the specified rating and clear codes before condemning components
Related powertrain codes
Frequently asked questions
What is Bank 2 on my engine?
Bank 2 is the cylinder bank that does NOT contain cylinder #1. On a V6 or V8 engine this is one of the two banks; on an inline engine there is no Bank 2 and P0331 would not apply. Check a cylinder-numbering diagram specific to your engine if unsure.
Can a P0331 code indicate real engine damage?
Yes. If the ECM is detecting vibration patterns consistent with knock but cannot suppress it via timing retard, it may indicate worn rod bearings, excessive carbon deposits on pistons, or other mechanical issues on Bank 2. A compression test and inspection are warranted if the sensor and wiring check out.
How is P0331 different from P0330?
P0330 is a general circuit malfunction on KS2 (the sensor circuit is not functioning at all), while P0331 is a rationality/performance fault — the circuit is active but the signal response is implausible or out of range during knock events.
Does incorrect fuel cause P0331?
Low-octane fuel can trigger genuine knock events that are too severe for the ECM to correct with timing retard, which in turn can push the knock sensor response outside its expected range and set P0331. Using the manufacturer-specified octane rating eliminates this as a variable during diagnosis.
Disabling P0331 in software
RaceTune can permanently disable P0331 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
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