Diagnostic article Generic OBD-II
P2856: Clutch-two pressure charge performance depends on its control state
P2856 evaluates pressure above the clutch-two model, with a separate hold-state criterion and explicit transition exclusions.
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Documented application
2025 GM 25OBDG07A Part 2 documented monitor only; its application-matrix filename join is unresolved. No model, engine or universal calibration 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.
P2856 is clutch-two pressure control too high in this GM transmission. The controller compares the sensor reading with modeled pressure and can diagnose excessive positive error through several branches. The generic charge-performance title does not mean every high pressure reading is abnormal regardless of the command.
Hold pressure has its own test
When the target is within approximately 0.051 bar of the hold-pressure value, the source flags measured-minus-modeled pressure above approximately 1.199 bar for 300 ms. Hold is the region intended for a clutch not transmitting torque. Other positive-error branches use different calibration-dependent thresholds and timing.
Exclude special control phases
Relevant sensor and valve electrical faults must be absent, and the redundant shutdown valve must be hydraulically on. Recovery and adaptive overrides are excluded. Superfill must be inactive and finished more than 80 ms earlier. Those conditions are essential when comparing a stored event with a subsequent test.
Record the actual control state, model output and pressure together, rather than treating one pressure number as a diagnosis. The source explains why the controller judged pressure excessive but does not determine whether the underlying cause is sensing, valve control or another hydraulic element. Applicable service information is required for component isolation.
Document scope and source
2025 GM 25OBDG07A Part 2 documented monitor only; its application-matrix filename join is unresolved. No model, engine or universal calibration applicability is inferred. These figures explain the cited controller logic, not a vehicle-specific repair instruction. Match the vehicle’s service information before applying them.
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
Clutch B Pressure Charge Performance
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