Powertrain, generic · Ignition system or misfire

P0333 Knock/Combustion Vibration Sensor B Circuit High

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. P0333 means the diagnostic DC voltage at the sensor input is too high – typically a short to voltage. GM sets it above 39 % of 5 V in 50 of 63 samples, in the first trip; Ford checks actively once every 250 engine cycles on modules with this circuit.

Likely causes

Signal or return wire shorted to voltage
Corrosion or moisture in the connector
Sensor faulty internally
Engine module internal

Symptoms

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

Repair estimate

DifficultyMediumDIY possible
Parts and labour€30–600
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

P0330P0331P0332P0328P0324

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