What goes wrong
The knock sensor detects abnormal vibrations (knocking or pre-ignition) within the engine. When the sensor reports an abnormally high voltage, the Engine Control Unit (ECU) interprets this as severe engine knocking and triggers a P0328 code. This often causes the ECU to retard ignition timing significantly to protect the engine, leading to a noticeable decrease in power and fuel efficiency.
Symptoms to watch for
- Check Engine Light illuminated
- Reduced engine power
- Poor fuel economy
- Engine hesitation or stumbling under acceleration
- Engine pinging or knocking sounds (less common, as ECU retards timing)
Root cause
The most common cause is a faulty knock sensor itself, which can degrade over time due to heat cycling and vibrations. Wiring issues, such as a damaged harness or corroded connector, can also lead to an intermittent or constant high signal. In rare cases, severe actual engine knocking from other issues could trigger the code, but the sensor failing is far more common.
Buy time with these
- • Monitor engine light and address promptly to prevent long-term engine issues from retarded timing or actual knocking.
Permanent fix
- Replace the faulty knock sensor with a new OEM or high-quality aftermarket unit.
- Inspect and repair any damaged wiring or corroded connectors to the knock sensor.
FAQ
What causes knock sensor failure (p0328)?
The most common cause is a faulty knock sensor itself, which can degrade over time due to heat cycling and vibrations. Wiring issues, such as a damaged harness or corroded connector, can also lead to an intermittent or constant high signal. In rare cases, severe actual engine knocking from other issues could trigger the code, but the sensor failing is far more common.
How much does it cost to fix?
National average $200–$400.
Is this a DIY repair?
Difficulty 4/5. Replace the faulty knock sensor with a new OEM or high-quality aftermarket unit.
What are the symptoms?
Check Engine Light illuminated; Reduced engine power; Poor fuel economy; Engine hesitation or stumbling under acceleration; Engine pinging or knocking sounds (less common, as ECU retards timing)