P0333
Knock Sensor 2 Circuit High
If your vehicle's onboard computer has flagged the diagnostic trouble code P0333, it refers to a detected anomaly regarding "Knock Sensor 2 Circuit High". This systemic engine fault needs a targeted check before symptoms expand.
Driver's Summary
The diagnostic trouble code P0333 indicates an active fault in the knock sensor 2 circuit high circuit or component. The most common signs are noticeable power loss on acceleration, check engine light. This is a moderate-severity fault — plan a repair shop visit within the week to keep it from escalating.
Symptoms
Noticeable power loss on acceleration, check engine light
Common Causes
- Short to voltage in Knock Sensor 2 circuit
- Defective knock sensor
- Mechanical engine noise triggering sensor
- PCM malfunction
How to Fix
- 1 Check wiring for shorts to power
- 2 Replace Knock Sensor 2
- 3 Inspect engine for excessive mechanical noise
- 4 Test PCM reference voltage
Technical Explanation
P0333 is stored after the control module confirms the fault over multiple ignition cycles, ruling out transient electrical noise as the cause. 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. After two failed drive cycles, the code transitions from a pending to a confirmed DTC, and the PCM activates the MIL. Clearing the code without repairing the fault will result in re-illumination within one to two complete drive cycles.
Is It Safe to Drive?
While the vehicle is typically drivable with P0333 active, avoid towing, aggressive acceleration, or extended highway driving until the fault is resolved. The primary risk is accelerated wear on short to voltage in knock sensor 2 circuit and defective knock sensor.
Mechanic's Pro Tip
The most common mistake with P0333 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: $250 - $650