Damaged, chafed or corroded wiring to the knock sensor, including open or short circuits; Poor connection at the sensor plug or control unit connector, such as corrosion, bent pins or water ingress; Faulty knock sensor, internally failed or cracked; Knock sensor loose or incorrectly torqued, or the mounting surface contaminated, giving a weak or noisy signal; Oil, coolant or heat damage to the harness near the engine block or intake manifold; Excess electrical interference from a faulty ignition component or poor earth; Fault inside the engine control unit.

P0325

Knock/Combustion Vibration Sensor A Circuit.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
3: AreaIgnition system or misfire
25: FaultThe specific fault in that area

What it means

P0325 is the generic code for a fault in the circuit of knock (combustion vibration) sensor A, usually bank 1 on engines with more than one sensor. The engine control unit sets it when the sensor signal is missing, out of range or implausible, or when the circuit shows an open or short. Without a usable knock signal the unit cannot detect detonation, so it normally retards ignition timing as a precaution.

Symptoms

Engine warning light on
Reduced power or sluggish acceleration
Poorer fuel economy
Pinking or rattling under load if detonation is not being controlled
Rough running or hesitation
Limp-mode style behaviour on some engines

Possible causes

Damaged, chafed or corroded wiring to the knock sensor, including open or short circuitslikely
Poor connection at the sensor plug or control unit connector, such as corrosion, bent pins or water ingresslikely
Faulty knock sensor, internally failed or crackedlikely
Knock sensor loose or incorrectly torqued, or the mounting surface contaminated, giving a weak or noisy signalpossible
Oil, coolant or heat damage to the harness near the engine block or intake manifoldpossible
Excess electrical interference from a faulty ignition component or poor earthrare
Fault inside the engine control unitrare

How to diagnose

Read the stored codes and freeze frame data to see engine load, speed and temperature when the fault set, and check for other codes
Visually inspect the knock sensor, its harness and the connector for chafing, oil soaking, heat damage, corrosion and water ingress
Check the sensor is fitted correctly and tightened to the manufacturer's torque, as the position and access vary by engine
Check the harness for continuity, short to earth and short to supply between the sensor and control unit, using the wiring diagram for that model
Measure the sensor's resistance or signal against the manufacturer's specification, as sensor type varies by engine
With a scope or live data, tap near the sensor and check for a response in the signal, and check for excess noise
Check the engine for mechanical noise or ignition faults that could be affecting the signal
Clear the code and road test, rechecking for return of the fault

How to fix

Repair or replace damaged wiring and fix any chafing or oil contamination of the harness
Clean, repair or replace the sensor connector and terminals
Replace the knock sensor if it is faulty, fitting it with the correct torque and a clean mounting surface
Refit or retorque a loose sensor to the manufacturer's specification
Repair ignition or earth faults found to be causing interference
Replace or repair the control unit only after all wiring and sensor checks have been completed and it is confirmed faulty

Can I keep driving?

Medium severity

The car can usually be driven for a short time to get it booked in, but expect reduced performance and economy. Avoid heavy loads and hard acceleration, since the engine may not be protected against detonation.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.