P0797Generic code

P0797 Code: Pressure Control Solenoid C Stuck On

The P0797 code means pressure control solenoid C in the automatic transmission is behaving as if it is stuck in the on position. It is usually caused by dirty or degraded fluid, or by wear in the valve body. The transmission can slip, shift harshly or drop into limp mode, so have it checked soon.

Severity
High
Can I keep driving?
Yes, but with caution
Estimated cost
$80 to $900
Difficulty
Hard
System
Transmission
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

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What the P0797 code means

Solenoids are electric valves that direct fluid pressure to the clutches and bands inside the transmission. Pressure control solenoid C regulates the pressure of another group of clutches in transmissions with many speeds. The transmission control module commands these solenoids and watches both their electrical circuit and the result, meaning the input and output shaft speeds.

The P0797 code is set when the solenoid behaves as if it were always on (stuck on). Electrically it can be perfectly fine, because the problem is hydraulic or mechanical. Wear particles in the fluid jam the solenoid valve or clog the passages in the valve body.

On any transmission code, the first check is the fluid: correct level using the manufacturer procedure (often with the engine running and at a specific temperature), a red or pink color and no burnt smell. Low or degraded fluid causes slipping, harsh shifts and solenoid or gear ratio codes that disappear once it is corrected.

This kind of fault is rarely solved with a multimeter, because everything looks right electrically. You have to compare what the part reports with reality: use a pressure gauge, a thermometer, a tachometer, or command the component with the scan tool and see whether the physical result matches the order.

See the P0700 guide to understand how transmission codes are read and why you need a scan tool that can talk to the transmission module.

P0797 code symptoms

  • Check engine light or transmission warning light on.
  • Shifts that are harsh, late or that do not happen at all.
  • Limp mode: the transmission stays in one fixed gear (often 2nd, 3rd or 4th).
  • Slipping or high rpm in certain gears.

Likely causes of the P0797 code

  1. Degraded fluid or fluid full of particles. The most common cause of stuck solenoids.
  2. Wrong fluid level. Too low causes slipping, and too high causes foaming.
  3. Solenoid mechanically stuck by dirt.
  4. Worn valve body, which leaks pressure internally.
  5. Worn internal clutches in high mileage transmissions.

How to diagnose the P0797 code step by step

  1. Check the fluid level and condition using the manufacturer procedure.
  2. Read all the codes in the transmission module with a scan tool that can access it.
  3. Measure the solenoid resistance at the transmission connector and compare it with the manual.
  4. Check the insulation to ground. It should read infinite.
  5. Command the solenoid with the scan tool and listen for the click.
  6. Inspect the case connector for fluid inside it or green pins.
  7. Compare input and output speeds in every gear to see which gear is slipping.
  8. Run a line pressure test with a gauge, if the transmission has a test port.

How to fix the P0797 code

  • Change the transmission fluid and filter using the specified fluid.
  • Clean or replace the solenoid or the valve body.
  • Clear the adaptations and run the relearn procedure.
  • If the clutches are worn, the transmission needs a rebuild.

Technical reference data

  • Shift solenoids (on/off): roughly 10 to 30 ohms.
  • Pressure or linear solenoids (PWM control): roughly 3 to 8 ohms.
  • Normal transmission fluid temperature: 70 to 95 °C (158 to 203 °F).
  • These are approximate values: check the manufacturer data for your vehicle.

Brand-specific notes

On many transmissions the solenoids sit in the valve body, and you reach them by removing the pan. Some solenoids are sold only together with the valve body or with the integrated control module. After replacing solenoids or the valve body, you usually need to clear the adaptations and run a relearn with a scan tool.

P0797 on Aisin, Jatco, GM 6T and Ford 6R Transmissions

On these units the solenoids are in the valve body, and you get to them by dropping the pan.

P0797 on Volkswagen DSG

On the Volkswagen DSG and on many modern transmissions, the solenoids come built into the mechatronic unit (the valve body with its control module), so they are often not sold separately.

Frequently asked questions about P0797

What does the P0797 code mean?
It is a generic OBD2 code that means pressure control solenoid C is acting as if it were stuck on. The cause is usually hydraulic or mechanical, such as dirty fluid or a worn valve body, not an electrical fault.
Can I drive with a P0797 code?
With caution, and only as far as a shop. A transmission with the P0797 code can drop into limp mode, and driving like that for a long time wears it out.
Will a fluid change fix it?
Sometimes, especially on performance or stuck codes like this one. On electrical faults it will not.
Does the transmission have to come out?
Normally not. The solenoids are replaced by removing the pan or the valve body cover.
How much does it cost to fix P0797?
As a rough guide, between $80 and $900. It costs more if the transmission itself has to be repaired.
Will a P0797 code clear itself?
The light may go out if the fault does not return, but a solenoid stuck from dirt or wear usually comes back. Clearing the code without fixing the cause only hides it for a while.
What is the most common cause of P0797?
Degraded fluid or fluid carrying wear particles. They jam the solenoid valve or clog the passages in the valve body.

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