P0879 Transmission Fluid Pressure Sensor/Switch D Circuit Intermittent

P0879 indicates an intermittent pressure sensor or switch D circuit fault. The D pressure signal drops out, spikes, or becomes invalid only sometimes.

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 clear intermittent pressure sensor D faults without reproducing the signal loss or instability.

Symptoms of P0879

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 P0879

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

Record pressure sensor D data during road vibration, hot operation, shift events, and harness movement to capture intermittent faults.
Inspect internal harness clips, case connector pins, fluid intrusion, terminal tension, sensor connector fit, and heat-sensitive opens.
Compare the intermittent pressure signal with pressure-control commands, gear ratio changes, slip events, and freeze-frame conditions.

Related OBD-II codes

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