P284D: Rod-one drift can be detected directly or through repeated correction

P284D is the rod-one drift monitor in this transmission. One route detects position outside wide tolerance bands for the current logical gear. The controller first requires agreement between the logical gear and speed-derived engagement, with no commanded rod force, no position-sensor electrical or consistency fault and no active synchronizer shift.

The controller also watches its own corrections

A second route counts at least ten activations of rod-one drift correction. Another flags correction remaining active for more than five seconds. Those corrections begin at narrower position limits than the direct drift check, so the code can reflect repeated intervention rather than one large excursion.

The direct route uses a 500 ms confirmation interval and excludes position-learning routines. This makes ordinary commanded movement during learning a different event.

Preserve the route that triggered

Record rod position, logical gear, supporting speed evidence and the correction counter or timer. A normal position after an intervention may conceal why the controller had to keep correcting it. The generic unrequested-movement title does not identify a specific worn fork or hydraulic defect. Applicable service documentation is needed to interpret the learned tolerances and isolate the physical cause before selecting a repair.

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.

GM physical PDF page 1047.