Diagnostic article Generic OBD-II
P0333: knock sensor B high-circuit sampling
P0333 monitors a high filtered output from knock sensor 2, identified by the catalog as sensor B.
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Documented application
2025 GM 25OBDG07A Part2 diagnostic monitor documentation; the application-matrix filename mismatch is unresolved, so no model or engine applicability is inferred.
The code alone does not identify a failed part or establish that a vehicle is safe to drive. Confirm the vehicle, reporting module and applicable service procedure.
P0333 monitors a high filtered output from knock sensor 2, identified by the catalog as sensor B. The source interprets the condition as a short-to-battery pattern, not a command to change fuel grade or ignition timing.
The test is periodic
Filtered output must exceed 4.7 volts while engine speed exceeds 500 rpm. Three events are required, with two-trip reporting. The diagnostic runs every 15 to 120 seconds according to engine speed, and the source specifies a 0.5 low-pass filter gain.
That schedule matters when assessing an intermittent complaint. A normal display between scheduled checks does not prove what the controller observed during the qualifying events, and three events cannot be assumed to occupy only three seconds.
Distinguish neighboring diagnostics
The same page separately lists the sensor-2 low-output and open-load checks. The open-load assessment has different speed, load, duty-cycle, and event requirements. Passing one branch does not automatically verify all three electrical classifications.
Confirmation should establish that the high-circuit branch completed with acceptable filtered output and correct sensor identification. The source explains the electrical evidence but does not identify a wire, connector, or sensor as the proven cause, and its thresholds are not a substitute for the applicable circuit-testing procedure.
Documentation and applicability
These details describe the monitor in GM’s 2025 25OBDG07A Part2 file. Its application-matrix filename does not match the download index, so model and engine applicability remain unresolved. Use the vehicle’s correct service information before applying these calibration details.
Article source documents
Source checks describe how the text was prepared; they do not certify a diagnosis or confirm compatibility with every vehicle using this code.
Original code reference
Dictionary definition
Knock/Combustion Vibration Sensor B Circuit High
This definition retains its original catalog scope. The article above is limited to its explicitly documented application.
Reference scope
Generic OBD-II definition.
A manufacturer label does not establish the model, year, engine or module to which a diagnosis applies. Read the safety and diagnostic limits.
Definition source
- DTC Database: pinned community code definitions
Source checked · MIT