OBD-II trouble code
P0797: Pressure Control Solenoid "C" Stuck On
The transmission control module detected that pressure control solenoid C is stuck in the on position, so its pressure stays high. Expect harsh, firm shifts or lost torque-converter engagement — address it promptly.
Quick facts
- System
- Powertrain
- Category
- Transmission / Pressure Control
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $150 – $900
- DIY difficulty
- Shop recommended
What does P0797 mean?
P0797 sets when the transmission control module (TCM) or PCM commands pressure control solenoid "C" to change state and the solenoid stays stuck in its energized, or "on," position. Instead of modulating pressure as commanded, the solenoid holds its circuit at a fixed high pressure — the module detects the discrepancy between the pressure it asked for and the pressure it's getting and stores the code.
Pressure control solenoid C is a third pressure-regulating solenoid in the valve body. Which physical solenoid is labeled "C" varies by transmission, so confirm the assignment in the manufacturer's service data before working on it. When it's stuck on, the affected shifts land hard and firm; depending on what circuit solenoid C controls, symptoms can also include disabled shift functioning, the torque converter clutch failing to engage, slippage, and overheating. That's the opposite of P0796, where the solenoid is stuck off and can't build pressure.
The cause is often mechanical rather than electrical. The coil frequently tests fine, and the real problem is debris, varnish, or a burr holding the valve applied so it won't return. Dirty or degraded fluid promotes exactly this kind of sticking, which is why fluid condition matters and a fluid and filter service is a sensible first step. Diagnosis then covers the solenoid's electrical health and free movement, and finally the valve body. The vehicle usually still drives, but harsh shifting and overheating stress the transmission, so fix it promptly.
Common causes
- Debris or varnish holding the solenoid valve in the applied position
- Dirty or degraded transmission fluid promoting valve sticking
- Mechanically failed or seized pressure control solenoid C
- Worn or contaminated valve body keeping the solenoid from returning
- Electrical fault commanding the solenoid on continuously
- Restricted transmission filter contributing to contamination
- Faulty transmission control module in rare cases
Symptoms
- Check engine light on with P0797 stored
- Harsh, firm, or abrupt shifts
- Torque converter clutch not engaging in some designs
- Transmission slipping or overheating
- Falling into limp mode in some cases
- Reduced fuel economy when shifts are mistimed
Diagnostic steps
- 1.Check transmission fluid level and condition first — dirty fluid is a leading cause of a sticking solenoid and the cheapest thing to rule out.
- 2.Confirm in the manufacturer's service data which physical solenoid is labeled "C" for this transmission.
- 3.Scan for companion transmission codes; a general P0700 confirms the TCM has stored transmission faults.
- 4.Read line-pressure live data if the transmission supports it, and compare commanded versus actual pressure.
- 5.Inspect the solenoid connector and harness, then resistance-check solenoid C and verify it moves freely where possible.
- 6.If the solenoid tests good, inspect the valve body for varnish, debris, or bore wear keeping the valve applied.
Repair cost
$150 – $900
A transmission fluid and filter service ($150-$350) is the first step and sometimes frees a sticking valve. A pressure control solenoid replacement runs roughly $250-$700 depending on whether it's externally accessible or requires dropping the pan or valve body. Valve-body cleaning or replacement is the higher end. Confirm fluid condition before replacing internal parts.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with transmission shift solenoid replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
Leave this one to a qualified shop. It typically involves emissions-critical components, refrigerant handling, or other work that requires manufacturer-grade tooling, training, or certification. DIY attempts often produce a more expensive problem than the original code.