Diagnostic article Generic OBD-II
P04DF: bank-1 purge-valve response during intrusive testing
P04DF monitors the bank-1 canister purge valve for a stuck-open pattern in the cited source.
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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.
P04DF monitors the bank-1 canister purge valve for a stuck-open pattern in the cited source. It uses the effect of a deliberately commanded opening on bank-1 intake-manifold pressure rather than relying only on a static tank-pressure measurement.
What qualifies the failure
The failure counter increases when the pressure difference from the beginning to the end of valve activation is below 5 hPa. At least three counts qualify, with one-second spacing between events. The table lists two-trip reporting and restricts the monitor to one completion per drive cycle.
The diagnostic therefore needs a commanded event and an observed before/after response. A general claim that purge is occurring cannot replace the specific pressure-change evidence used by this monitor.
Scope of the interpretation
The row requires released purge operation and warm-environment conditions, including coolant above 69.75°C and ambient temperature above −7.5°C. One enable label unexpectedly refers to integrated bank-2 flow, and the mixture-correction inequalities are ambiguous. Those details require calibration confirmation rather than silent correction.
Verification should focus on the documented bank-1 response and the applicable completed test. The base code does not prove that the valve is mechanically stuck or identify an external hose leak. The correct service procedure must distinguish the source of insufficient response before any repair choice.
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
EVAP System Purge Control Valve A Performance/Stuck Open
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