OBD-II trouble code
P0331: Knock Sensor 2 Circuit Range/Performance (Bank 2)
The bank 2 knock sensor is producing a signal that doesn't behave the way the computer expects — present, but implausible or out of the normal range.
Quick facts
- System
- Powertrain
- Category
- Knock & Other
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $150 – $600
- DIY difficulty
- Intermediate DIY
Browse every code in P0300–P0394, or start from the full code library.
What does P0331 mean?
Knock sensors are piezoelectric "microphones" bolted to the engine block that listen for detonation (knock/ping) so the computer can pull ignition timing before it damages pistons. Knock sensor 2 serves bank 2 — the cylinder bank without cylinder 1. P0331 sets when that sensor's signal fails the computer's plausibility checks: it's not open or shorted (those set P0332/P0333), but the output is out of the expected range or doesn't respond the way a healthy sensor should.
Common real-world causes are a sensor that has drifted or cracked, a loose or over/under-torqued sensor (they must be torqued to spec to couple properly with the block), corrosion in the connector adding resistance, or chafed wiring picking up interference. Because a distrusted knock sensor forces the computer to run conservative, retarded timing, the usual symptom is quietly reduced power and economy rather than any drama.
On many V6/V8 engines these sensors live under the intake manifold, which is why labor — not the part — dominates repair cost, and why doing both sensors at once is often smart.
Common causes
- Failed or drifted knock sensor (bank 2)
- Loose or improperly torqued sensor — poor mechanical coupling
- Corroded connector or high-resistance terminals
- Chafed or degraded sensor wiring/shielding
- Coolant or oil intrusion into the sensor connector (common under intake manifolds)
- Rarely, a PCM fault
Symptoms
- Check engine light on
- Reduced power and sluggish acceleration (retarded timing)
- Worse fuel economy
- Possible audible pinging under load if knock protection is compromised
- Often no obvious symptom at all
Diagnostic steps
- 1.Scan and record freeze-frame; check for companions (P0325-P0334 family).
- 2.Inspect the bank 2 knock sensor connector and wiring — many live under the intake, where coolant spills and corrosion collect.
- 3.Measure resistance across the bank 2 sensor's terminals against the published figure. Comparing it with the bank 1 sensor is a weaker check than it looks, since both drift together with age and heat, and an in-spec reading proves nothing either way — a piezo element fails by losing output sensitivity rather than by changing resistance. What actually separates a drifted sensor from a good one is a tap test on AC millivolts with the connector off, run on both banks and compared: the response, not the resistance, is what a range/performance code is complaining about.
- 4.Confirm the sensor is torqued to spec — over- or under-torque skews its response.
- 5.Rule out genuine persistent knock (bad fuel, carbon, lean condition) making the signal look abnormal.
- 6.Replace the sensor if it fails testing; consider replacing both if the intake must come off.
Repair cost
$150 – $600
The sensor itself is $30-$120, but on many engines it sits under the intake manifold, pushing labor to 2-4 hours. Doing both sensors while the intake is off adds little cost and avoids repeating the labor.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with knock sensor replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.