P0325: Knock/Combustion Vibration Sensor A Circuit
What to do
Expect slightly reduced performance and economy. If the sensor was recently replaced, mention it — incorrect mounting torque is a common reason the code returns.
What this code means
A circuit fault in knock sensor A, which on a V engine is the bank 1 sensor and on an inline engine with two is the one nearer the front.
The name in the title is the standard's, and it is not what most scan tools say. A tool, a workshop manual or a parts catalogue is far more likely to call this Knock Sensor 1, Bank 1 — and it is the same sensor. The standard moved to lettered designators and added combustion vibration to the name because on many diesels the identical part is used to confirm that combustion happened at all rather than to catch detonation. The corpus transcribes the standard's title and explains the older name here, since a page that quietly renames a part is a page somebody cannot find.
These sensors are piezoelectric and generate their own signal, so they are unusually sensitive to mounting: torque matters, and a sensor that is loose, over-tightened or fitted with anything between it and the block will not hear the engine properly. That makes installation error a genuine cause rather than a footnote — a sensor replaced without the specified torque frequently sets the same code again.
Likely causes
Start here
- Faulty knock sensor · moderate
- Incorrect knock sensor mounting torque · moderate
- Corroded or loose connector · easy
- Open circuit in sensor wiring · moderate
Rare
- Failed control module · specialist
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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