Diagnostic article Generic OBD-II
P033D: knock circuit high with an unresolved sensor label
P033D is cataloged as knock/combustion-vibration sensor D circuit high, but the supplied GM row calls the channel knock sensor 3.
Read before applying this article
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.
P033D is cataloged as knock/combustion-vibration sensor D circuit high, but the supplied GM row calls the channel knock sensor 3. This mismatch must be resolved before assigning the code to a physical sensor.
What can still be read reliably
The row describes a short-to-battery check using filtered output above 4.7 volts with engine speed above 500 rpm. It lists three events and two-trip reporting. The periodic schedule is 15 to 120 seconds depending on engine speed, with a stated low-pass filter gain of 0.5.
These details distinguish the electrical test from the reference-level rationality check on the following page. They also show that three qualifying events are not a fixed three-second timer.
What remains unsuitable for application
The surrounding P033C and P033A rows repeat the sensor-3 wording, while the subsequent reference check names sensor 4. This pattern supports flagging an inconsistent channel label rather than silently selecting one interpretation.
Use the correct vehicle’s DTC and wiring information to establish the monitored channel. Verification then needs a completed high-circuit test for that confirmed channel. This draft remains needs-review because the source does not reliably settle the sensor identity, and it offers no component-location or replacement instruction.
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 D 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