What it means
The TCM detects that pressure control solenoid C remains energized hydraulically despite commanded de-energization. Line pressure or shift quality deviates from target.
At a glance
- Usually lights the check-engine light
How it works
Pressure control solenoid C controls hydraulic pressure when the TCM energizes or de-energizes it. P0797 sets when the TCM commands solenoid C off but detects that its hydraulic effect remains on, which can make pressure or shift behavior differ from the target.
Common causes
Most likely first.
- Solenoid mechanically stuck
- Valve body contamination
- Carbon or debris buildup preventing free movement
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
- Check freeze-frame and live data for solenoid C commands and pressure or shift behavior when the TCM commanded it off.
- Verify transmission fluid level and condition using the vehicle's specified method, and note contamination that could obstruct solenoid movement.
- Inspect the solenoid C connector and wiring for damage or faults that could keep the solenoid energized despite the command.
- Test the solenoid C circuit and operation against the TCM command using the manufacturer's procedure.
- If electrical control is correct, inspect solenoid C and its valve body passage for sticking, debris, or restricted movement.
Common fixes
- Repair wiring or connector faults that keep solenoid C energized.
- Correct fluid level or service contaminated fluid as specified for the vehicle.
- Clean the valve body passage if debris is preventing solenoid C from moving freely.
- Replace pressure control solenoid C if it remains mechanically stuck after inspection.
Can I keep driving?
Limit driving if shifts are harsh or the vehicle slips, and avoid towing or heavy acceleration because abnormal pressure can worsen shift and clutch damage. Stop if the transmission loses drive or shifts unpredictably.
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.