Damaged or corroded knock sensor wiring, connectors, or terminals; Faulty knock sensor itself, often due to internal failure or damage from engine heat and vibration; Poor electrical connection at the sensor or ECM, including loose pins or water intrusion; Shorted or open circuit in the knock sensor harness, sometimes caused by chafing or rodent damage; Failed ECM, although this is less common and should be diagnosed last; Engine mechanical issues that produce excessive vibration or noise, mimicking a sensor fault

DTC codes / P03xx · Ignition system and misfire / P0327

P0327Knock Sensor 1 Circuit Low Input (Bank 1)

Q: What does code P0327 mean?

Knock Sensor 1 Circuit Low Input (Bank 1). P0327 indicates that the engine control module (ECM) has detected a low voltage signal on the knock sensor circuit for bank 1, which is the side of the engine containing cylinder number one. The knock sensor is a piezoelectric device that generates a small voltage when it detects engine vibration, and the ECM uses this signal to adjust ignition timing and prevent damaging detonation.

P0327 indicates that the engine control module (ECM) has detected a low voltage signal on the knock sensor circuit for bank 1, which is the side of the engine containing cylinder number one. The knock sensor is a piezoelectric device that generates a small voltage when it detects engine vibration, and the ECM uses this signal to adjust ignition timing and prevent damaging detonation.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaIgnition system and misfire

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
Reduced engine performance and fuel economy due to the ECM retarding ignition timing as a protective measure
Audible engine knocking or pinging under acceleration, especially when climbing hills or carrying a load
Rough idle or hesitation during acceleration in some cases
In rare instances, the engine may enter limp mode to prevent potential damage

Common causes, most likely first

Damaged or corroded knock sensor wiring, connectors, or terminals
Faulty knock sensor itself, often due to internal failure or damage from engine heat and vibration
Poor electrical connection at the sensor or ECM, including loose pins or water intrusion
Shorted or open circuit in the knock sensor harness, sometimes caused by chafing or rodent damage
Failed ECM, although this is less common and should be diagnosed last
Engine mechanical issues that produce excessive vibration or noise, mimicking a sensor fault

How to diagnose and fix it

Inspect the knock sensor wiring and connector for damage, corrosion, or loose connections, and repair as needed
Check the sensor's mounting bolt for proper torque and ensure the sensor is clean and free of debris
Measure the resistance of the knock sensor with a multimeter and compare to the manufacturer's specification
Perform a voltage drop test on the sensor circuit to identify excessive resistance
If the sensor fails testing, replace it with a quality part and clear the code
If the code persists after sensor replacement, diagnose the ECM and its programming, looking for technical service bulletins (TSBs) for known issues
Verify the repair by test-driving the vehicle and ensuring the code does not return

Don't overlook the simple checks first

A loose knock sensor mounting bolt is a surprisingly common cause of P0327, as it can create a poor ground and low signal voltage.
Aftermarket knock sensors can be overly sensitive or fail prematurely, so using an OEM-quality sensor is often worth the extra cost.
The ECM may set P0327 due to a poor ground connection at the engine block, not just the sensor circuit itself.
Excessive engine noise from a failing lifter or exhaust leak can sometimes trigger knock sensor codes, so listen for other abnormal sounds.
Some vehicles require a relearn procedure after knock sensor replacement, so consult the factory service information to avoid a repeat code.

Can I keep driving with P0327?

It is generally safe to drive with P0327, but avoid aggressive acceleration or heavy loads, as the ECM may not be able to properly control ignition timing, which could lead to engine damage over time. Have the fault diagnosed and repaired promptly to maintain optimal performance and fuel economy.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.