P0328
Knock Sensor 1 Circuit High
The appearance of the standard OBD2 trouble fault code P0328 is an indicator that your vehicle ECU triggered a threshold alert for "Knock Sensor 1 Circuit High". Understanding the root component breakdown helps avoid expensive diagnostic fees.
Driver's Summary
A P0328 fault code points directly to a problem with knock sensor 1 circuit high that the ECM has confirmed over multiple drive cycles. Typical symptoms include check engine light, sluggish performance, engine pinging. While the car is usually drivable, you should schedule a diagnosis within the next few days to prevent the issue from worsening.
Symptoms
Check engine light, sluggish performance, engine pinging
Common Causes
- Short to battery voltage in knock sensor wiring
- Internal failure of knock sensor
- Actual severe engine knock
- Over-tightened knock sensor
How to Fix
- 1 Repair wiring short to power
- 2 Replace Knock Sensor 1
- 3 Diagnose internal engine mechanical issues
- 4 Loosen and correctly retorque the sensor
Technical Explanation
Code P0328 is confirmed when the ECM's diagnostic algorithm detects a parameter deviation that persists across a defined number of consecutive drive cycles. For injector-specific codes, the ECM monitors the injector control circuit voltage drop during each pulse; a shorted or open injector presents a characteristic resistance signature that differs measurably from a healthy unit. The MIL illuminates after the fault is confirmed on two consecutive drive cycles, and the freeze frame data captured at first detection is stored in the PCM's memory for diagnostic reference.
Is It Safe to Drive?
You can drive short distances, but the symptoms — check engine light, sluggish performance, engine pinging — indicate the affected system is compromised. Leaving this unresolved will lead to progressively worse fuel economy and potential damage to components beyond the original fault.
Mechanic's Pro Tip
The most common mistake with P0328 is replacing the sensor without verifying the reference voltage and ground integrity first. Use a scan tool to monitor the sensor's live output; a truly failed sensor shows a stuck, flatlined reading — a sensor that fluctuates but reads slightly off usually indicates a wiring or vacuum issue, not a dead sensor. Always spray electrical contact cleaner on the connector pins before condemning the sensor.
Knock sensor replacement: $200 - $600