What P0325 means
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.
How the engine computer detects it
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).
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- Check engine light on
- Loss of power, sluggish response from ignition retard
- Higher fuel consumption
Common causes
- Wiring or connector chafed, broken or corroded (sensor often under the intake manifold) Most likely
- Knock sensor faulty (cracked piezo, moisture, heat damage) Possible
- Sensor loose or wrongly torqued Possible
- Engine software or diagnostic calibration Less likely
- Engine module input stage Less likely
How to diagnose P0325
- Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
- Inspect the parts involved: knock sensor a, knock sensor wiring, engine control module.
- Work through the causes above from most to least likely, cheapest checks first.
- Clear the code and drive a full drive cycle to confirm the repair held.
Vehicles that report P0325 most
| Vehicle | Years | Reports | Share | Median miles |
|---|---|---|---|---|
| Chevrolet Cruze | 2014–2018 | 4 | — |
Counts of owner complaints to the NHTSA that mention P0325 (15 in total), not failure rates: popular models get more complaints simply because more of them are on the road. Models with fewer than 3 complaints are left out.
Reading the code
- P
- Powertrain
- 0
- Generic (SAE) code
- 3
- Ignition system or misfire
- 25
- Specific fault
Questions drivers ask
Can I drive with code P0325?
Usually yes for a short time, if the car drives normally, the temperature gauge reads normal and the check engine light is steady. If the light flashes, the engine loses power or overheats, or other warning lights come on, pull over and have it checked.
Will my car pass an emissions inspection with P0325?
Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.
Can I fix P0325 myself?
Often yes, with an OBD-II scanner and basic tools. Difficulty: medium. Start with the cheapest checks before replacing expensive parts.
This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.