P0855 Drive Switch Input Circuit High

P0855 indicates a high drive switch input circuit. The drive-range input is stuck high, open, or shorted to voltage compared with expected logic.

Code details

Generic OBD-II · P0

System: Transmission
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not treat a high drive switch input as a hydraulic engagement problem until the circuit is repaired.

Symptoms of P0855

Harsh, delayed, or slipping shifts, or being stuck in one gear.
Check-engine light, sometimes with limp-home mode.
Flaring RPM or a shudder under load.

Common causes of P0855

Low or degraded transmission fluid.
A failing speed sensor, shift solenoid, or pressure-control circuit.
Wiring, connector, or internal hydraulic/mechanical faults.

Useful checks before replacing parts

Check drive switch signal voltage, ground integrity, connector fit, open circuits, short-to-voltage faults, and switch adjustment.
Compare scan-tool drive input status with actual shifter movement and range sensor data across all selector positions.
Inspect harness areas disturbed by shifter, console, or transmission service and verify the circuit under load.

Related OBD-II codes

These nearby transmission entries can help compare wording and pin down the fault area.