P0849 Transmission Fluid Pressure Sensor/Switch B Circuit Intermittent

P0849 indicates an intermittent transmission fluid pressure sensor or switch B circuit fault. The B pressure input becomes invalid under certain conditions.

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 rely on a parked idle reading for an intermittent pressure sensor B fault; road-test data is usually needed.

Symptoms of P0849

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 P0849

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

Monitor pressure sensor B data during the shift or load condition stored in freeze-frame data and look for sudden dropouts.
Inspect sensor B wiring, case connector terminals, shared reference or ground circuits, fluid intrusion, and internal harness movement.
Compare pressure sensor B behavior with pressure-control commands, fluid temperature, slip, and companion pressure-switch codes.

Related OBD-II codes

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