P0331 Code Meaning and Next Steps

First checks take 10 to 15 minutes for the first checks. No special tools are usually needed for the first checks.

Can you keep driving?

Stop driving if any of these apply

!The engine is audibly knocking or pinging hard under load.
!The engine starts running much worse or the warning light flashes.

If the light is steady and the vehicle still drives normally: Usually yes for a short time, but it should not be ignored if the engine is pinging or running badly.

What to check first

Step-by-step checks

1
Free - no tools
Check for loose connector fitment, cracked wiring, or damage near the knock sensor harness
2
Free - no tools
Notice whether the engine is pinging, because real detonation can sometimes distract from the sensor issue
3
Basic tool needed
If live data is available, compare knock counts and timing correction with engine load
4
Basic tool needed
Confirm whether recent engine work changed sensor mounting torque or routing
5
Basic tool needed
If the code appeared after a repair, inspect the harness first before replacing the sensor

If the code returns

-If the signal stays low with a known-good harness, the sensor or mounting surface moves up the list.
-If the code returns after a connector repair, check for a deeper wiring break or poor sensor contact.
-If the engine is actually knocking, fix the cause of that before assuming the sensor is the only problem.

Background

What this code means

P0331 is a generic OBD-II knock-sensor code for knock sensor 2.

A low knock-sensor signal can come from a sensor issue, wiring fault, or a mounting problem that keeps the sensor from hearing normal engine vibration.

The ECU may pull timing less or more than expected, or the engine may feel slightly less responsive under load.

Diagnosis

Common causes

Most common

Weak knock sensor signal

The ECU may not be getting enough input from the sensor.

Common

Connector or wiring issue

A bad connection can make the sensor look low.

Common

Mounting problem

A loose or isolated sensor may not pick up normal vibration.

Possible

Engine noise or noise filter issue

Real engine noise can confuse the monitoring logic.

Avoid these mistakes

What not to do

xDo not ignore pinging, rattling under load, or poor fuel quality just because the code names a sensor.
xDo not replace both knock sensors before checking the wiring and confirming which bank is actually affected.

Parts

Parts that may need replacing

PartTypical costNotes

Knock sensor$40-$160Relevant when the sensor is truly weak or biased low.

Connector pigtail repair$15-$90Worth checking if the connector or pins are damaged.

Engine tuning or intake repair$20-$300Relevant if the engine is actually pinging or noisy.

Related OBD codes

P0326

P0326 usually means knock sensor 1 is reporting an out-of-range or performance problem.

P0328

P0328 usually means knock sensor 1 is reading too high.

P0329

P0329 usually means knock sensor 1 is responding intermittently.

P0332

P0332 usually means knock sensor 2 is reading too high.

Source notes

Generic OBD-II (SAE J1979 / ISO 15031-5). P0331 was expanded around common low knock-sensor signal faults, including wiring issues, mounting problems, and sensor bias.

This guide is written as a generic multi-make reference, so bulletin history, sensor locations, and repair order can still change by manufacturer and engine family.

This is generic OBD-II guidance and should not override vehicle-specific service information. Exact diagnosis and repair steps vary by make, engine family, and model year.

Last reviewed: 2026-04-10

Reference: Open reference

P0331 - P0331 Usually Means Knock Sensor 2 Is Reading Too Low