P0325 fault code: Knock Sensor 1 Circuit
Last updated · OBDCode UK editorial
You can usually keep driving carefully for now. Watch for new noises, pinking under load, warning lights, or loss of power, and book a garage diagnosis soon — especially before your MOT.
Can I DIY?
Caution — conditions apply. We do not publish DIY repair or strip-down steps for this code on this page. Read codes and observe only; leave the repair to a qualified garage.
Some checks may be possible for a careful DIY driver with the right tools and a safe place to work. Stop if anything feels beyond your skill or kit.
What does P0325 mean?
P0325 is a generic (SAE standard) powertrain code reported by your car’s engine control unit. It sits in the P03xx block, which covers ignition system and misfire. The stored description is “Knock Sensor 1 Circuit”. The code itself tells you which circuit or system tripped the fault — not always the exact part that failed.
How to diagnose P0325 yourself
- Confirm P0325 and companion ignition codes: Scan while the car is parked. Record whether P0325 is current or pending, freeze-frame engine speed and load, and any P0300-family or cam/crank codes. Do not clear the memory yet. Stop if: The engine management light is flashing or the engine is juddering — stop driving and arrange recovery.
Park safely and switch off before locating the socket. Its position varies, so use the vehicle handbook and never force or dismantle trim. - Listen for pinking from the driver’s seat: On a short, legal road in open air — not a closed garage — note whether you hear a light metallic pinking on gentle acceleration. Do not perform a wide-open-throttle test. Do not open the bonnet to tap the block. Stop if: The noise is heavy knocking, power drops, or the light starts flashing. Never idle this check in a closed garage.
- Do not strip the knock sensor: If a forum or generic guide tells you to unbolt the sensor from the block, stop. Access often needs undertrays or engine mounts. This page does not publish fitting or torque steps. Stop if: You would need axle stands, an undertray off, or to support the engine to reach the sensor.
Will P0325 fail an MOT?
An illuminated engine management light is a Major defect at MOT (automatic fail) until the fault is repaired and the light stays off.
Before booking your test, check what usually fails on your car: see our MOT pass rates by make and model, built from 33.1 million DVSA tests.
What the MOT data says
No MOT certificate item corresponds to this code; MOT outcome data cannot be shown.
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P0325 — quick answers
Is it safe to drive with P0325?
Drive with care. You can usually keep driving carefully for now. Watch for new noises, pinking under load, warning lights, or loss of power, and book a garage diagnosis soon — especially before your MOT.
Can I fix P0325 myself?
Caution — conditions apply. We do not publish DIY repair or strip-down steps for this code on this page. Read codes and observe only; leave the repair to a qualified garage. Basic tools only — for example a household socket set, tyre gauge, or a consumer OBD reader.
Will P0325 fail my MOT?
An illuminated engine management light is a Major defect at MOT (automatic fail) until the fault is repaired and the light stays off.
Fault-code identifiers are standard diagnostic facts. Their explanations and diagnostic guidance on this site are original editorial summaries, not reproduced SAE wording. MOT defect rules reflect the DVSA MOT inspection manual (2026). This page is general guidance for UK drivers, not a substitute for a professional diagnosis.