P0327: Knock Sensor 1 Circuit Low (Bank 1 or Single Sensor)
The signal from knock sensor 1 is weaker than the engine computer expects, often because of a wiring fault or a failed sensor.
What P0327 means
P0327 is a more specific version of P0325. The engine computer has measured a knock sensor 1 signal that is below its low limit. A piezo knock sensor makes a small voltage when the engine vibrates, so a reading that stays too low points to an open wire, a short, a corroded connector or a dead sensor. A sensor bolted on with the wrong torque can also send a weak signal, because it needs firm contact with the block to hear vibrations. On many V6 and V8 engines the sensor and its harness sit in the valley under the intake manifold, where coolant and oil leaks can corrode the connector. Since the computer cannot trust the knock signal, it often retards timing to stay safe, which costs a bit of power and mileage. Shops measure sensor resistance, check the wire to the computer for continuity, and tap the block near the sensor while watching its output on a scope. Fix the wiring first if it is damaged.
Common symptoms
- Check engine light on
- Slight loss of power
- Lower fuel economy
- Pinging under load in some cases
- Often no noticeable change
Most common causes
- Open or shorted knock sensor wire
- Corroded connector
- Failed knock sensor
- Sensor bolt loose or torqued wrong
- Harness damage under the intake manifold
What to check yourself first
Find where your knock sensor is mounted. If it is accessible, check that the connector is clean and latched and the wire is not cut or chafed. Make sure no one has recently worked near it and left it unplugged.
Typical fixes and what they cost
| Fix | Typical cost | Note |
|---|---|---|
| Replace knock sensor | $417-$589 | Torque matters; an overtightened or loose sensor gives a weak signal. |
| Electrical diagnosis to find a wiring or connector fault | $122-$179 | For an open wire or bad connector. |
| Replace intake manifold gasket (when removed for access) | $683-$834 | On engines where the sensor is under the intake, the gasket is replaced when the manifold comes off. |
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
- P0325 Knock Sensor 1 Circuit (Bank 1 or Single Sensor)
- P0330 Knock Sensor 2 Circuit (Bank 2)
- P0335 Crankshaft Position Sensor "A" Circuit
- P0300 Random/Multiple Cylinder Misfire Detected
- P0171 System Too Lean (Bank 1)