The P0779 code in your 2020 Mercedes-Benz GLC indicates an electrical fault in the pressure control solenoid B circuit within the 9G-TRONIC 9-speed automatic transmission. This code specifically identifies wiring or driver circuit issues.
9G-TRONIC Electrical Architecture
Mercedes' 9-speed transmission uses sophisticated electronic controls. Pressure control solenoid B's electrical circuit connects through the mechatronic unit to vehicle wiring. P0779 indicates a problem in this electrical path.
Common Electrical Fault Sources
- Open circuit in solenoid B wiring
- Short to ground in circuit
- Short to battery voltage
- Connector pin corrosion
- TCM output driver failure
- Internal mechatronic harness damage
Symptoms of P0779
- Check engine light on
- Transmission warning message
- Shift quality issues
- Pressure regulation problems
- Possible limp mode
- Comfort compromised
Mercedes Diagnostic Access
Mercedes-Benz transmissions require XENTRY or Star Diagnostic equipment for full access. Circuit-level testing and component control requires factory-level diagnostics.