Pressure Control Solenoid C Stuck On
The transmission control module (TCM) or powertrain control module (PCM) has detected that transmission pressure control solenoid 'C' is stuck in the 'on' position. This indicates that the solenoid is continuously directing hydraulic fluid pressure to a specific circuit even when the computer commands it to turn off.
A stuck pressure control solenoid can cause severe drivability issues, erratic shifting, and potential internal transmission damage if driven extensively. It should be diagnosed and repaired immediately to prevent further mechanical failure.
Common symptoms
- Illuminated Check Engine Light
- Harsh or erratic transmission shifting
- Transmission slipping between gears
- Vehicle stuck in 'limp mode' (limited to a single gear)
- Delayed engagement when shifting into drive or reverse
Likely causes
- Dirty, contaminated, or degraded transmission fluid
- Defective transmission pressure control solenoid 'C'
- Clogged hydraulic passages inside the transmission valve body
- Damaged wiring or loose connections in the solenoid circuit
- Internal transmission mechanical failure
- Faulty Transmission Control Module (TCM)
What to check before replacing parts
Check the transmission fluid level and condition.
Look for: Look for low fluid levels, burnt smell, or dark/metallic contamination which indicates poor fluid quality causing the solenoid to stick.
Inspect the wiring harness and connectors for pressure control solenoid C.
Look for: Check for frayed wires, melted insulation, corroded pins, or loose connections that could cause a short to power.
Perform a resistance test on pressure control solenoid C using a multimeter.
Look for: Compare the measured ohms to the manufacturer's specification; an out-of-range reading or a short to ground/power indicates a failed solenoid.
Use a bi-directional scan tool to command the solenoid on and off.
Look for: Listen for an audible click from the transmission pan or monitor the pressure PID to see if the solenoid physically responds to the command.
Perform a transmission line pressure test with a mechanical gauge.
Look for: Compare the actual hydraulic pressure against the scan tool data and manufacturer specs to determine if the valve body or pump is failing.
This page explains the generic P0797 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
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