Draft guidance: awaiting Claude spot-check, qualified-mechanic review and named-editor approval. Do not use a fault code alone to replace parts.

P0325: Knock sensor 1 circuit malfunction

The control module has found an electrical fault or implausible signal in knock-sensor circuit 1, usually for Bank 1 or the sole sensor.

What P0325 means

The control module has found an electrical fault or implausible signal in knock-sensor circuit 1, usually for Bank 1 or the sole sensor. It does not prove that the sensor itself has failed, nor does it necessarily mean the engine is physically knocking.

Can I still drive?

If the light is steady and the engine sounds and performs normally, a short, gentle journey to a garage is usually the sensible limit. Avoid towing, hard acceleration, high revs and prolonged heavy load because knock control may be restricted. Stop and recover the car if there is metallic pinging or knocking, overheating, severe hesitation, a flashing warning light or rapidly worsening performance.

Symptoms

  • Engine-management light with no other obvious symptom.
  • Sluggish acceleration or reduced power.
  • Hesitation under load and poorer fuel economy.
  • Possible metallic pinging or knocking.

Common causes

  • Failed knock sensor.
  • Open, shorted, heat-damaged or chafed wiring.
  • Loose, wet or corroded connector.
  • Incorrect installation or tightening after previous work.
  • A supply, earth or control-module input fault.
  • Genuine detonation or unrelated mechanical noise confusing the signal.

Safe first checks

  • Read all codes and retain freeze-frame data. Once the engine is cool and the ignition is off, inspect accessible sensor wiring and connectors for loose pins, damaged insulation, corrosion, fluid contamination or signs of recent disturbance. Check for low coolant, overheating history and obvious intake leaks without opening a hot cooling system. Do not strike the engine as a makeshift sensor test or apply generic resistance values; designs and specifications vary.

Typical UK fix cost

Expect about £90–£180 for diagnosis and roughly £160–£450 total for an accessible sensor or loom repair. Sensors buried beneath an inlet manifold may raise the total to £350–£800. Any underlying overheating or internal-engine fault is additional.

Related models

This is a generic OBD-II code used across many makes and models. The exact test thresholds, component layout and repair route vary by engine and manufacturer, so check vehicle-specific technical information before ordering parts.

Related fault codes

Sources

A diagnostic trouble code identifies a system or circuit to investigate. It does not prove that a named part has failed. Preserve freeze-frame data and seek a vehicle-specific diagnosis before clearing the code.