Faulty pressure control solenoid 'C' internally shorted or open; Damaged, chafed, or corroded wiring in the solenoid circuit; Loose or contaminated electrical connector at the solenoid or TCM; Transmission fluid contamination or degradation causing solenoid malfunction; Failed transmission control module (TCM) or internal circuit fault; Low transmission fluid level or clogged filter affecting solenoid operation

DTC codes / P07xx · Transmission / P0798

P0798Pressure Control Solenoid 'C' Electrical

Q: What does code P0798 mean?

Pressure Control Solenoid 'C' Electrical. P0798 indicates that the transmission control module (TCM) has detected an electrical fault in the circuit for pressure control solenoid 'C', which is used to regulate hydraulic pressure inside the automatic transmission. The computer monitors the solenoid's electrical current and voltage and sets this code when the readings fall outside the expected range, indicating an open circuit, short circuit, or excessive resistance.

P0798 indicates that the transmission control module (TCM) has detected an electrical fault in the circuit for pressure control solenoid 'C', which is used to regulate hydraulic pressure inside the automatic transmission. The computer monitors the solenoid's electrical current and voltage and sets this code when the readings fall outside the expected range, indicating an open circuit, short circuit, or excessive resistance.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyProfessional

AreaTransmission

Symptoms you may notice

Illumination of the check engine light or transmission warning light, often with no other noticeable symptoms
Harsh or delayed gear shifts, especially when the transmission is cold or under load
The transmission may enter limp mode, limiting vehicle speed and gear selection
Slipping between gears or a sudden loss of power during acceleration
Erratic shifting patterns or failure to downshift when passing
In some cases, the vehicle may refuse to shift out of a particular gear

Common causes, most likely first

Faulty pressure control solenoid 'C' internally shorted or open
Damaged, chafed, or corroded wiring in the solenoid circuit
Loose or contaminated electrical connector at the solenoid or TCM
Transmission fluid contamination or degradation causing solenoid malfunction
Failed transmission control module (TCM) or internal circuit fault
Low transmission fluid level or clogged filter affecting solenoid operation

How to diagnose and fix it

Check transmission fluid level and condition; top off or replace fluid if contaminated
Inspect the solenoid 'C' electrical connector for corrosion, tightness, and cleanliness
Test the solenoid 'C' circuit for continuity and resistance using a multimeter, comparing to manufacturer specifications
Check wiring harness for chafing, breaks, or shorts between the solenoid and TCM
If resistance is out of specification, replace pressure control solenoid 'C'
Clear the code and test-drive the vehicle to verify the repair and ensure the code does not return
If the code persists after solenoid replacement, diagnose the TCM and internal transmission wiring

What most technicians overlook with P0798

A faulty solenoid 'C' can sometimes be caused by debris in the transmission fluid, so flushing the fluid may resolve the issue without parts replacement.
The TCM may set P0798 due to a momentary voltage spike or low battery voltage, so always check the charging system and battery condition before condemning the solenoid.
On some vehicles, the pressure control solenoid 'C' is part of the valve body assembly and cannot be replaced separately, requiring a more extensive repair.
A code for solenoid 'C' does not always mean the solenoid itself has failed; the TCM or internal wiring can be the culprit, especially if multiple solenoid codes are present.
Intermittent connections at the transmission pass-through connector are a common cause that can be missed during a simple resistance check.

Can I keep driving with P0798?

Driving with P0798 is generally possible but not recommended for long distances, as the transmission may enter limp mode or shift harshly, increasing wear. Avoid heavy acceleration or towing, and have the vehicle diagnosed promptly to prevent further transmission damage.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.