Powertrain, generic · Ignition system or misfire

P0329 Knock/Combustion Vibration Sensor A Circuit Intermittent

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 A is the first sensor (bank 1 or a single sensor). With a fault the module retards ignition across the board as protection – noticeable loss of power and higher consumption. P0329 reports brief dropouts of the sensor signal – loose contacts, a wire breaking with engine movement and heat, or a loose sensor. No manufacturer document with a threshold for this code was found; GM and Ford cover such faults with their circuit codes, so the description follows CARB's input monitoring requirement.

Likely causes

Loose contact, spread pins or corrosion in the connector
Wire chafing only with engine movement or heat
Sensor loose or wrongly torqued
Sensor or engine module faulty

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 aknock sensor wiringengine control module

Related codes

P0325P0326P0327P0334P0324

References: law.cornell.edu, wiki.ross-tech.com, bosch-mobility.com.