Powertrain, generic · Ignition system or misfire

P0331 Knock/Combustion Vibration Sensor B Circuit Range/Performance

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

The knock sensor is a piezoelectric structure-borne sound sensor bolted to the engine block; the module evaluates its signal per cylinder and retards ignition when it detects knock. Sensor B is the second sensor – bank 2 on V engines, but on some four-cylinders also bank 1. With a fault the module retards ignition across the board as protection – noticeable loss of power and higher consumption. P0331 means the circuit is electrically sound but the signal is implausible. GM sets it when the filtered background noise stays below a threshold – typically a loose sensor or one not bolted down properly – in the first trip; Saab's GM-based engines also when excessive knock persists on several cylinders or a whole bank for 8–10 s. Ford does not use this code.

Likely causes

Sensor loose, wrongly torqued or mounted with sealant or on a dirty surface
Engine software or calibration (bulletins for some models)
Genuine knock on a whole bank or mechanical noise
Sensor aged or damaged (low sensitivity)

Symptoms

  • Check engine light on
  • Loss of power, sluggish response from ignition retard
  • Higher fuel consumption

Repair estimate

DifficultyMediumDIY possible
Parts and labour€0–400
Time0.5–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

knock sensor bknock sensor wiringengine control module

Related codes

P0330P0332P0333P0326P0324

References: gsi.ext.gm.com, saabwisonline.com, saabwisonline.com, static.nhtsa.gov.