P0955 Auto Shift Manual Mode Circuit

P0955 indicates an auto shift manual mode circuit fault. The module cannot reliably identify or enter the manual shift mode request state.

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 diagnose shift timing until the manual mode enable circuit is confirmed.

Symptoms of P0955

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 P0955

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

Compare manual mode switch data with actual selector position, upshift and downshift inputs, range data, and gear display behavior.
Inspect mode switch wiring, shifter connector fit, spilled-liquid damage, reference voltage, ground, and module communication data.
Check whether the issue affects mode entry only, individual shift requests, or the display of selected gear.

Related OBD-II codes

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