Powertrain, generic · Ignition system or misfire

P0327 Knock/Combustion Vibration Sensor A Circuit Low

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. P0327 means the diagnostic DC voltage at the sensor input is too low – the signal or return wire is shorted to ground. GM biases each input through a resistor network and sets the code below 8 % 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. Subaru introduced a more durable sensor for this fault.

Likely causes

Signal or return wire chafed to ground
Moisture or corrosion in connector or sensor
Sensor faulty internally (series issue on some models)
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.

What to check first

  1. Inspect connector
  2. Check wiring continuity
  3. Replace sensor if faulty

Parts involved

knock sensor aknock sensor wiringengine control module

Related codes

P0325P0326P0328P0332P0324

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