P0778: Pressure Control Solenoid B Electrical
What to do
The transmission has probably fallen back to a protective pressure setting, so expect harsh shifts or a fixed gear. Drive it gently to a garage rather than any distance.
What this code means
A measurable electrical fault in pressure control solenoid B's circuit. Like solenoid A, this is current-controlled rather than switched, so the module compares commanded current against actual and can detect a partially failed winding rather than only a dead one — which means the code can appear while the transmission still broadly works.
Likely causes
Start here
- Faulty pressure control solenoid · moderate
- Short circuit in a transmission solenoid · moderate
- Fluid tracking into the transmission connector · moderate
Less common
- Damaged transmission wiring harness · moderate
Rare
- Faulty transmission control module · specialist
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
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