P0325 P0xxx · Powertrain (P) Medium severity
Knock Sensor 1 Circuit Malfunction (Bank 1)
The knock sensor signal is missing or out of range, so the ECU cannot detect detonation and will typically retard ignition timing as a protective default.
Severity guidance: Medium — drivability or emissions affected, book it in this week
Symptoms you will notice
- Reduced power
- Poor fuel economy
- Pinging under load
- No audible knock detection
Common causes
Ordered from most to least likely — start at the top.
- 1 Failed knock sensor
- 2 Damaged wiring (often rodent damage)
- 3 Loose mounting bolt changing the sensor's torque
- 4 Corrosion under the sensor
How to diagnose it
Cheapest and least invasive first — most of these codes are not a parts problem.
- ✓ Inspect the sensor harness — knock wiring is a favourite target for rodents.
- ✓ Check the mounting bolt torque; over- or under-torque changes the signal.
- ✓ Tap-test the sensor while watching the signal on a scope or live data.
- ✓ Measure resistance and check for a short to earth.
Repair options
- Replace the knock sensor and torque to specification
- Repair the harness
- Clean the mounting surface
P0325 — frequently asked questions
Is it safe to drive? +
Generally yes, but the engine runs with retarded timing — you lose power and economy until it is fixed.
Why must the bolt torque be exact? +
The sensor is a piezoelectric microphone; wrong torque changes its resonant frequency and the ECU misreads knock.
Confirm the diagnosis before you buy parts
Send us the code, freeze-frame data and the vehicle — our engineers will tell you what to test first.