What it means
Pressure control solenoid C shows intermittent electrical or hydraulic dropouts.
At a glance
- Usually lights the check-engine light
How it works
Pressure control solenoid C regulates hydraulic pressure in response to commands from the TCM. P0799 sets when solenoid C's electrical signal or hydraulic response drops out intermittently, often as a loose connection or harness fault changes with vibration.
Common causes
Most likely first.
- Loose connector at the transmission
- Connector with intermittent contact under vibration
- Harness routed against vibrating component
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
How to diagnose it
- Review freeze-frame data and graph solenoid C commands and related transmission readings to identify when the fault appears.
- Inspect the solenoid C connector for looseness, corrosion, fluid intrusion, or terminals that may lose contact under vibration.
- Trace the harness to check for rubbing, pinching, or contact with vibrating or hot components.
- Monitor live data while gently moving accessible wiring and the connector to see whether solenoid C operation or readings cut out.
- If no visible fault is found, test the solenoid C coil, circuit continuity, and hydraulic response for intermittent failure using the manufacturer's procedure.
Common fixes
- Secure the solenoid C connector and repair loose terminal contact.
- Clean or repair corroded or fluid-contaminated connector terminals.
- Reroute and secure the harness away from vibration, heat, or rubbing.
- Repair damaged wiring or replace solenoid C if testing identifies an intermittent fault.
Can I keep driving?
Limit driving if the fault causes slipping, harsh shifts, or missed gears, and avoid heavy loads until the intermittent control loss is found. Stop if the transmission loses drive or shifts unpredictably, since repeated slipping can increase damage.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.