P0873 Transmission Fluid Pressure Sensor/Switch C Circuit High

P0873 indicates a high input from transmission fluid pressure sensor or switch C. The pressure feedback signal is above the expected range.

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 condemn hydraulic parts before checking pressure sensor C wiring and whether pressure is actually high.

Symptoms of P0873

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 P0873

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 for short-to-voltage, open ground, connector damage, internal harness faults, or pressure sensor C stuck high.
Compare pressure data with commanded pressure, gear state, fluid temperature, and shift feel.
Review pressure-control solenoid and line-pressure codes that may explain actual high pressure.

Related OBD-II codes

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