Pressure control solenoid C sticking due to dirt, varnish or metal debris in the fluid; Worn, contaminated or incorrect transmission fluid, or low fluid level; Faulty solenoid, with an internal electrical fault or a coil that is failing; Damaged wiring, corroded connector or short to power or earth in the solenoid circuit; Worn or sticking valve body bores, or a blocked or collapsed filter restricting pressure control; Internal clutch wear causing ratio errors that the control unit interprets as a stuck solenoid; Faulty transmission control unit or mechatronic unit driver.

P0797

Pressure Control Solenoid C Stuck On.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
7: AreaTransmission
97: FaultThe specific fault in that area

What it means

P0797 is the generic SAE J2012 code for Pressure Control Solenoid C stuck on in the automatic transmission. The transmission control unit has detected that the solenoid is permanently energised or passing hydraulic pressure when it has not been commanded, usually shown by gear ratio errors, slip or abnormal pressure feedback. Which clutch or function 'C' controls depends on the make, model and gearbox.

Symptoms

Gearbox warning light or engine management light on
Harsh, delayed or flared gear changes
Gearbox stuck in one gear or in limp-home mode
Slipping or loss of drive in certain gears
Poor fuel economy or high engine revs at cruising speed
Transmission overheating

Possible causes

Pressure control solenoid C sticking due to dirt, varnish or metal debris in the fluidlikely
Worn, contaminated or incorrect transmission fluid, or low fluid levellikely
Faulty solenoid, with an internal electrical fault or a coil that is failinglikely
Damaged wiring, corroded connector or short to power or earth in the solenoid circuitpossible
Worn or sticking valve body bores, or a blocked or collapsed filter restricting pressure controlpossible
Internal clutch wear causing ratio errors that the control unit interprets as a stuck solenoidpossible
Faulty transmission control unit or mechatronic unit driverrare

How to diagnose

Read all stored codes and freeze frame data, noting gear, temperature, speed and load when the fault set, and look for other gearbox codes
Check the transmission fluid level and condition, following the manufacturer's procedure for temperature and method, as many units are sealed
Inspect the gearbox wiring harness and connector for chafing, fluid ingress, corrosion and pin damage
Measure the solenoid resistance and check the circuit for shorts and continuity against the manufacturer's specification
View live data for commanded and actual solenoid current or pressure, and gear ratio, to see whether the solenoid is truly stuck on
Check for software updates or technical bulletins for the specific model and gearbox
Drop the pan or open the valve body, if the design allows, to inspect the filter, magnet and debris
Road test and check the clutch slip and ratio data to separate hydraulic faults from mechanical wear

How to fix

Repair or replace damaged wiring or connectors in the solenoid circuit
Replace the faulty pressure control solenoid, or the valve body or mechatronic assembly if the solenoid is not supplied separately
Change the transmission fluid and filter with the specified fluid, and clean or replace the valve body if contaminated
Correct the fluid level and repair any leaks
Overhaul or replace the gearbox if internal wear or debris damage is found
Apply a manufacturer calibration update only where a bulletin lists a software fault as a known cause, then carry out any required adaptation reset

Can I keep driving?

Medium severity

The car can usually be driven gently a short distance, but the gearbox may go into limp mode and continued use risks clutch and gearbox damage. Have it diagnosed soon and avoid towing or heavy loads until it is fixed.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.