P0325: Knock Sensor 1 Circuit (Meaning, Causes, Fixes)
What P0325 means
A knock sensor is bolted or threaded into the engine block and listens for detonation ('knock' or 'pinging'), where the air/fuel mixture ignites in a way that wastes power and can damage the engine if it goes on. When the sensor reports knock, the engine computer (PCM) retards ignition timing in steps until the knock stops. P0325 is a generic code that applies to all OBD-II vehicles. RepairPal defines it as Knock Sensor #1 circuit malfunction (single sensor or bank 1) and says it sets when the sensor 1 circuit readings are too low, too high, erratic, or otherwise outside their normal window. The two sources differ on the likely causes: OBD-Codes.com points to the sensor, the wiring, or a failed PCM, while RepairPal adds an EGR fault, a cooling system problem and a lean air/fuel ratio, and lists replacing the knock sensor when the real cause was cooling or EGR as common misdiagnoses. OBD-Codes.com notes the code seems to show up more often on Honda, Acura, Nissan, Toyota and Infiniti vehicles, and that it may come and go or stay on constantly. P0325 appears in the 2026 carfaultcodes.co.uk review of UK fault code data.
Severity: can I keep driving?
Drive with caution, fix soon
RepairPal rates P0325 'Moderate': it usually isn't an immediate safety risk, but get it diagnosed within a reasonable time. If you hear pinging or knocking under load, or the temperature gauge reads hotter than normal, ease off and have it checked sooner, because prolonged knocking can damage the engine.
Common symptoms
- Check engine light on (RepairPal says it may or may not light; OBD-Codes.com says it can be intermittent)
- Pinging or knocking from the engine, especially when accelerating or under load
- Lack of power or hesitation (listed by OBD-Codes.com)
- Worse fuel economy (listed by OBD-Codes.com)
- Engine running hotter than normal (listed by RepairPal)
- Sometimes no noticeable symptoms (noted by RepairPal)
Likely causes
Roughly most to least common, based on the sources below. Your vehicle may differ.
- Failed knock sensor
- Damaged, shorted or open wiring or connector in the knock sensor circuit
- EGR system malfunction (listed by RepairPal)
- Cooling system problem (listed by RepairPal)
- Lean air/fuel ratio (listed by RepairPal)
- Failed engine computer (PCM), which is less common (listed by OBD-Codes.com)
Diagnostic steps you can do
Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.
- Read all stored codes. Lean codes (P0171, P0174), EGR codes (such as P0401) or coolant temperature codes (such as P0128) alongside P0325 point away from the sensor itself.
- Read the freeze frame data with a scan tool to see the conditions when the code set; both sources recommend it.
- Check coolant level and condition and oil level, as RepairPal's diagnostic steps do, to rule out an overheating or mechanical problem first.
- Inspect the knock sensor wiring and connector for broken, frayed or corroded wires and repair anything you find.
- If you have a multimeter and the factory spec, check the sensor's resistance and the wiring continuity from the PCM to the sensor connector, as OBD-Codes.com describes. Specs vary by vehicle, so use the service manual's figure.
Typical fixes
- Repair damaged wiring or a bad connector in the knock sensor circuit
- Replace the knock sensor if testing shows it has failed
- Fix an EGR fault, cooling problem or lean condition if that's the real cause
- Diagnose and replace the PCM only after the sensor and wiring check out
Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.
🛠 When to call a pro
- The engine is audibly knocking or running hot, which can lead to engine damage
- The knock sensor is buried under the intake manifold on your engine, which makes replacement a big job
- You've replaced the sensor and the code came back, which RepairPal flags as a common misdiagnosis
- Watching the knock sensor and timing advance data live needs a data-streaming scan tool, as RepairPal's shop procedure uses
Where to buy
Plain search links. Always match parts to your exact year, make, model and engine.
FAQs
Will a new knock sensor fix P0325?
Not always. OBD-Codes.com lists wiring faults and, less often, the PCM as causes, and RepairPal lists replacing the knock sensor when the real problem was the cooling system or EGR system as common misdiagnoses.
Can I drive with P0325?
RepairPal rates it 'Moderate', meaning it may not affect safety right away but should be diagnosed in a reasonable time. If the engine is pinging or running hot, get it checked sooner, since prolonged knocking can damage the engine.
What's the difference between P0325 and P0330?
P0325 is the circuit fault for knock sensor 1 (bank 1 or the only sensor). P0330 is the same fault for knock sensor 2, which on V-type engines is usually the bank 2 sensor. OBD-Codes.com lists P0330 as a related knock sensor code.
Why does a knock sensor code cause poor performance?
When the PCM can't trust the knock sensor, it may retard ignition timing to protect the engine, as OBD-Codes.com explains. Less timing advance means less power and worse fuel economy.
Sources
Last reviewed 2026-10-22. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.