Diagnostic article Generic OBD-II
P284F: Rod-three drift uses even-side gear evidence and correction history
P284F combines direct position drift with repeated or prolonged correction on rod three, while excluding known sensor faults.
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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.
P284F is the rod-three unrequested-movement implementation in this transmission. Its direct drift check compares position with tolerance bands for the logical gear, but only after the gear agrees with speed-derived engagement. The source uses even-clutch and output-speed information for this rod.
Valid feedback is a prerequisite
The controller excludes rod-three electrical and consistency faults, active synchronizer shifting and position-learning routines. No rod force must have been present for the required interval. These conditions matter because commanded movement or already-untrusted feedback should not be mistaken for the same mechanical drift finding.
The direct branch confirms an out-of-band condition over 500 ms. Separate routes track at least ten drift-correction activations or correction lasting more than five seconds. The corrective control begins at narrower limits than the direct test.
What to retain after a correction
A position brought back toward target may no longer show the original excursion. Preserve the correction counter, active time, logical gear and corroborating speeds with the event. The summary does not provide universal position limits or prove that a fork, valve or other internal part is defective. Use the applicable transmission service information to distinguish the underlying cause.
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
Shift Fork C Unrequested Movement
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