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. P0325 means the sensor circuit is open or the signal stays below the noise threshold. GM feeds a 20 kHz test signal into the circuit and detects an open circuit when it does not cancel out, setting the code in the first trip; Ford sees any open or short as a knock signal that is too small compared with the speed- and load-dependent noise level (at least 1,500 rpm, 35 % load, warm engine). Bulletins name moisture in the sensor (VW Touareg 3.6), engine software (GM Malibu 1.5) and chafed wiring (FCA).
Medium severity. Can I keep driving?You can drive carefully, without towing or putting heavy loads on the engine at low RPM. Ignition timing will be more retarded and fuel consumption slightly higher, and without knock monitoring the engine has less of a safety margin.
Symptoms
- Check engine light on
- Loss of power, sluggish response from ignition retard
- Higher fuel consumption
Most likely causes
- Wiring or connector chafed, broken or corroded (sensor often under the intake manifold)
- Knock sensor faulty (cracked piezo, moisture, heat damage)
- Sensor loose or wrongly torqued
- Engine software or diagnostic calibration
- Engine module input stage
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It affects emissions.
What each character of P0325 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 3: Ignition and misfires
- 25: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0325?
You can drive carefully, without towing or putting heavy loads on the engine at low RPM. Ignition timing will be more retarded and fuel consumption slightly higher, and without knock monitoring the engine has less of a safety margin.
What causes code P0325?
The most common causes are: wiring or connector chafed, broken or corroded (sensor often under the intake manifold); knock sensor faulty (cracked piezo, moisture, heat damage); sensor loose or wrongly torqued.
Related codes
- P0326Knock/Combustion Vibration Sensor A Circuit Range/Performance
- P0327Knock/Combustion Vibration Sensor A Circuit Low
- P0328Knock/Combustion Vibration Sensor A Circuit High
- P0330Knock/Combustion Vibration Sensor B Circuit
- P0324Knock/Combustion Vibration Control System Error
Sources
- gsi.ext.gm.com: 18OBDG03A Engine Diagnostics
- newtonnet.co.uk: fordobd2012
- saabwisonline.com: dtc p0325 p0327 p0328 p0330 p0332 or p0333
- static.nhtsa.gov: SB 10069616 2280
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.