Diagnostic article Generic OBD-II
P2781: A downshift input-high fault concerns voltage, not a held paddle
P2781 detects the TAPDN input above its electrical limit for a defined interval, subject to controller supply conditions.
Read before applying this article
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.
P2781 identifies an electrically high downshift-paddle input in the cited GM controller. The source lists a threshold above 4,774 mV, 30 mV hysteresis and a confirmation time of at least 150 ms. This is a voltage-window check, not a timer measuring how long the driver holds the paddle.
Supply conditions affect the result
The monitor operates with battery voltage above 8.75 V and below 18 V. The engine must not be cranking and the key state must not be stop. P0882 and P0883 disable evaluation. Those prerequisites should accompany any conclusion that a later test has passed.
Keep the input and command distinct
A downshift command can be valid even though the high electrical limit is never approached; the two concepts are not interchangeable. Verification should retain raw TAPDN voltage during release and operation, together with monitor status. A normal recognized switch state observed later cannot rule out an earlier high-voltage interval.
The source does not establish a universal paddle connector or component location. Apply the vehicle’s circuit information to distinguish a switch issue from wiring or controller-input behavior. The code reports what the input did, rather than proving which component must be replaced.
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
Downshift Switch Circuit High
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