P0815: an upshift request remains active too long

P0815 diagnoses an upshift switch state stuck in the active tap-up position in the cited TCM. The documented response disables tap or manual up/down operation. It is an input-state fault, not a direct finding that the transmission cannot mechanically upshift.

Duration depends on the enabled branch

The displayed first path requires the tap-up state to persist beyond one second after qualifying range conditions. The table lists forward drive ranges as enabled for that path, with Park, Neutral and Reverse excluded, and requires more than one second since a range change.

A second path begins on the page with a 120-second timing threshold and different continuing prerequisites. This article does not transfer the first path's one-second rule to every selector state or switch architecture.

An active request is not an illegal voltage

The monitor excludes P0826 in active, pending and current-key-cycle failure states. That matters because P0826 represents an illegal out-of-range switch state, while P0815 concerns a recognized upshift request that lasts too long.

Record switch state through press and release, selected range and related code status. A tap-up command persisting after release is more informative than a momentary valid request. Verification should confirm appropriate state release and a passing enabled diagnostic using the exact vehicle procedure. The source does not identify whether the physical switch, its circuit or processing caused the persistent state, and it supplies no mandatory shifter replacement.

Source and applicability

Documented monitors in gm-2025-03a, model year 2025. These are module/calibration examples; vehicle, engine and transmission applicability must be confirmed independently. GM 2025-03a, page 1124.