P0778 Pressure Control Solenoid B Electrical

P0778 points to an electrical fault in pressure control solenoid B. The circuit is abnormal before hydraulic diagnosis should take priority.

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 components until the pressure-control solenoid B circuit has been tested electrically.

Symptoms of P0778

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 P0778

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 pressure control solenoid B power, control circuit, internal harness, case connector, and terminal condition.
Measure circuit resistance or current using the transmission service procedure and compare with known-good circuits.
Inspect shared transmission power feeds and grounds when multiple pressure-control or shift-solenoid codes are present.

Related OBD-II codes

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