System: Powertrain (P-Code) Coverage: SAE Standard (Generic) Fault Family: knock_sensor_circuit

Code P0325: Knock/Combustion Vibration Sensor A Circuit

Diagnostic & Technical Explanation

Code P0325 (Knock/Combustion Vibration Sensor A Circuit) sets when the ECM detects an open circuit, out-of-range voltage, or a total loss of signal from a knock (combustion vibration) sensor used to retard timing and protect the engine from detonation, or when the overall knock control system itself reports an internal error. Physical causes are a failed piezoelectric sensor element, an improperly torqued sensor (knock sensors are torque-sensitive and read incorrectly if over- or under-tightened), or chafed/corroded wiring between the sensor and the ECM.

Probability-Ranked Repair Procedures (4 Ranked Fixes)

Rank #1

Inspect and reseat the knock sensor connector

Easy DIY

Parts Estimate: $5.0–$15.0 USD Labor Estimate: 0.4 Shop Hours

1. Locate the knock sensor(s), usually threaded into the block under the intake manifold
2. Unplug and inspect for oil contamination or corroded pins
3. Clean contacts and reseat the connector
4. Clear the code and monitor knock counts on a scan tool

Required Replacement Parts: 🔧 Electrical contact cleaner

Rank #2

Replace the knock sensor at correct torque spec

Moderate DIY

Parts Estimate: $30.0–$100.0 USD Labor Estimate: 1.2 Shop Hours

1. Remove the intake manifold or components blocking sensor access
2. Unbolt the failed knock sensor
3. Install the replacement and torque to the exact factory spec (over- or under-torquing causes false readings)
4. Reconnect, clear codes, and verify signal activity while revving the engine

Required Replacement Parts: 🔧 Knock (combustion vibration) sensor

Rank #3

Repair knock sensor circuit wiring

Professional Required

Parts Estimate: $10.0–$60.0 USD Labor Estimate: 1.3 Shop Hours

1. Back-probe the signal and shield/ground legs at the sensor connector
2. Voltage-drop test the harness back to the ECM
3. Repair chafed or corroded conductors with soldered, heat-shrunk, shielded splices
4. Confirm a clean knock signal waveform on a scope

Required Replacement Parts: 🔧 Shielded automotive wiring repair kit

Rank #4

Diagnose knock control module/ECM internal fault