P0325 — Knock sensor circuit malfunction (Bank 1 / Sensor 1)
The knock sensor circuit isn’t reading correctly — the engine may retard timing as a precaution.
What it means in plain English
P0325 indicates a knock-sensor circuit fault (bank/sensor numbering depends on the vehicle). The sensor detects detonation; a circuit fault can cause timing retard, power loss, or poor fuel economy. Wiring damage and failed sensors are both common; access labor varies a lot by engine.
Common causes
- Failed knock sensor
- Damaged wiring or connector
- Sensor contamination or incorrect torque on replacement
What you can safely check
- Note pinging under load if present.
- Access is often poor — many knock sensors are under manifolds; DIY is easy to underestimate.
Pull the code yourself (disclosed)
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A reusable Bluetooth OBD-II scanner lets you read the code and freeze-frame data before authorizing “mystery” diagnostics. One option: BlueDriver Bluetooth Pro OBD-II scan tool (BlueDriver/Levanta affiliate). Any capable OBD-II reader is fine — this is not required to use Fair Auto Shops.
When to go to a shop
Request circuit testing before parts. Labor can dominate the bill when the sensor is buried — ask for labor hours on the estimate.
Typical related repair costs (U.S. national averages)
These are related repairs shops may find after diagnosis — not a guaranteed bill for every P0325. Ranges exclude taxes, fees, diagnostics, and your location.
- $417–$589 national average for knock sensor replacement (RepairPal; estimates last updated September 3, 2026; excludes taxes/fees and location; source). Labor $291–$427; parts $126–$161.
Related cost guides: Knock Sensor
Questions to ask before you authorize work
Use questions before you authorize a repair and how to read a repair estimate. Watch for patterns in spotting upselling.
Find an honest independent shop
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FAQ
What should I do first with a P0325 code?
Photograph all codes, note symptoms and whether the light is flashing, avoid clearing data until a shop sees it, then use an independent shop with a clear diagnostic plan.
More check-engine codes
P0420 · P0430 · P0300 · P0301 · P0171 · P0174 · P0455 · P0456 · P0442 · P0446 · P0128 · P0401 · P0133 · P0113 · P0506 · P0507 · P0700 · P0741 · P0011 · P0340 · P0335 · P0101 · P0299 · P0135 · P0440 · P0441 · P0010 · P0500 · P0121
Hub: How to read a check-engine code · Repair cost guides · Affiliate disclosure