What are the common causes of P0778?

An open in the pressure control solenoid B wiring. A short to ground or power. Corrosion at the solenoid B connector. A failed solenoid B coil. A TCM driver fault.

Test the solenoid B circuit for continuity. Check the circuit for a short to ground. Measure the solenoid B resistance. Inspect the connector for corrosion. Replace the solenoid if the coil is off spec. Clear the code and retest.

P0778

Pressure Control Solenoid B Electrical

System: Transmission (P code)
Lamp: Check Engine Light
Category: Powertrain - Transmission

What it means

P0778 means Pressure Control Solenoid B Electrical.

Where it lives

For P0778, start at the solenoid the description names.

Check these first

An open in the pressure control solenoid B wiring
A short to ground or power
Corrosion at the solenoid B connector
A failed solenoid B coil
A TCM driver fault

What to do next

Test the solenoid B circuit for continuity
Check the circuit for a short to ground
Measure the solenoid B resistance
Inspect the connector for corrosion
Replace the solenoid if the coil is off spec
Clear the code and retest

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Updated

Generic SAE J2012 definition. Last updated 2026-10-10.