P0325: Knock Sensor 1 Circuit (Bank 1 or Single Sensor)
The engine computer sees a problem with the signal from knock sensor 1, which listens for engine pinging.
What P0325 means
A knock sensor is a small microphone bolted to the engine block. It picks up the sharp vibration of detonation, or pinging, which happens when fuel ignites too early under heat and pressure. The engine computer uses the signal to pull back spark timing just enough to stop the knock. RepairPal explains that P0325 means the readings from knock sensor 1 are too low, too high, erratic or outside their normal window. The sensor itself can fail, but wiring and connector problems are common, and RepairPal also lists EGR problems, cooling system faults and lean mixtures as triggers, because those can cause real knock. Without a working knock sensor, many computers retard timing as a precaution, so you may lose some power and mileage. Shops check the sensor resistance and output, inspect the harness and look for causes of real detonation. On V engines, sensors often live under the intake manifold, so confirming the diagnosis before replacing them saves money.
Common symptoms
- Check engine light on
- Pinging or knocking on acceleration
- Reduced power as the computer retards timing
- Lower fuel economy
- Engine may run hotter than normal
Most common causes
- Faulty knock sensor
- Damaged or corroded knock sensor wiring or connector
- Real engine knock from a lean mixture or overheating
- EGR system problem
- Loose sensor mounting bolt
What to check yourself first
Use the octane fuel your owner manual calls for. Check coolant level and look for signs of overheating. If the knock sensor is easy to reach on the side of the block, inspect its connector and wire for damage or corrosion.
Typical fixes and what they cost
| Fix | Typical cost | Note |
|---|---|---|
| Replace knock sensor | $417-$589 | On many V6 and V8 engines the sensors sit under the intake manifold, which drives up labor. |
| Electrical diagnosis to find a wiring or connector fault | $122-$179 | Harness damage and corroded connectors are common, especially when sensors sit in the engine valley. |
| Check engine light diagnosis at a shop | $125-$183 | RepairPal warns knock sensors get replaced when the real cause is a cooling system problem. |
Typical US price ranges for parts and labor, not quotes. Your shop should confirm the cause with a diagnostic before replacing parts.
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Related codes
- P0327 Knock Sensor 1 Circuit Low (Bank 1 or Single Sensor)
- P0330 Knock Sensor 2 Circuit (Bank 2)
- P0171 System Too Lean (Bank 1)
- P0401 Exhaust Gas Recirculation "A" Flow Insufficient Detected
- P0128 Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)