P0799 — Pressure Control Solenoid C Intermittent

OBD2 code P0799 flags a problem with the automatic transmission control (pressure control solenoid c intermittent). Short, gentle driving to a shop is usually possible. Common culprits: valve body wear, low or degraded transmission fluid, faulty transmission speed sensor.

powertrain (engine/transmission)

Is it safe to drive?

Drive with caution Drive only if the transmission still shifts predictably, and avoid highway speeds. Driving with slipping or limp mode accelerates internal wear — every kilometre can add to the final repair bill.

How to diagnose with an OBD scanner

Read the code and freeze frame Connect an OBD2 scanner, confirm P0799 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many P0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the automatic transmission control for damage, corrosion, chafing or poor contact.
Subsystem check Check transmission fluid level and condition — dark, burnt fluid points to internal wear.
Subsystem check Read transmission-specific codes and live data (solenoid states, input/output speed) with a capable scanner.
Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P0799 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for P0799 (parts and labor, USD, independent shop rates): Valve body repair or replacement: $700–$1,500; Replace a shift solenoid: $300–$800; Transmission rebuild or replacement: $2,500–$5,500; Transmission fluid service: $150–$350. Overall, fixing P0799 usually costs between $150 and $5,500. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

Will P0799 clear itself?

Sometimes P0799 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

What is the most common cause of P0799?

The most common causes are: valve body wear, low or degraded transmission fluid, faulty transmission speed sensor.

How much does it cost to fix P0799?

Valve body repair or replacement — $700–$1,500; Replace a shift solenoid — $300–$800; Transmission rebuild or replacement — $2,500–$5,500; Transmission fluid service — $150–$350. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

Is it safe to drive with P0799?

Drive only if the transmission still shifts predictably, and avoid highway speeds. Driving with slipping or limp mode accelerates internal wear — every kilometre can add to the final repair bill.

How do I diagnose P0799 myself?

Start with a scan: confirm P0799, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the automatic transmission control, and verify the suspect component against live data before buying parts.

When your vehicle's engine control module stores trouble code P0799, it means the powertrain control system has detected an irregular signal coming from the transmission's pressure control solenoid C. This solenoid plays a key role in managing hydraulic pressure inside your automatic transmission, which directly controls gear shifts and clutch engagement. The fault is classified as "intermittent," indicating the abnormality comes and goes rather than being permanently present. For the check engine light to activate, the PCM must observe this faulty behavior repeat itself under specific driving conditions multiple times.

The transmission control system relies on a network of solenoids, sensors, and hydraulic passages to execute smooth gear changes. When solenoid C sends erratic data to the control module—voltage spikes, dropouts, or unexpected resistance values—the module logs P0799 and captures a freeze frame snapshot. That snapshot records engine load, RPM, coolant temperature, and vehicle speed at the exact moment the fault occurred, giving you a roadmap for reproduction during diagnosis. Without resolving the underlying cause, the transmission may enter a protective limp mode, restrict shifting to certain gears, or develop worsening performance over time.

Common Symptoms of P0799

A noticeable shudder or vibration at highway speeds, especially under load
The transmission refusing to shift out of a single gear, signaling limp-home mode activation
Illumination of the check engine light or a dedicated transmission warning indicator
Gear changes that feel harsh, jerky, or uncharacteristically delayed
In severe cases, complete loss of forward or reverse movement
Unexpected slipping between gears, where the engine revs without corresponding acceleration

Likely Causes

Damaged, corroded, or loose wiring and connectors in the valve body harness
A failed or failing pressure control solenoid, including solenoid C specifically
Excessive wear on internal transmission components such as clutches or the torque converter
Low transmission fluid levels or fluid that has become dark, burnt, or contaminated
A faulty transmission input/output speed sensor feeding incorrect data to the control module
Wear or scoring on the valve body itself, affecting hydraulic flow paths

How to Diagnose P0799

Plug in an OBD2 scanner and confirm that P0799 is the active or stored code, then record all freeze frame data—this information pinpoints the driving conditions present when the fault first appeared.
Pull all additional trouble codes from the transmission and engine controllers; related codes often expose the root problem rather than the symptom. Check for any manufacturer technical service bulletins applicable to your specific make and model.
Perform a thorough visual inspection of the transmission wiring harness and electrical connectors, looking for frayed insulation, broken wires, corrosion buildup, or connectors that are not fully seated.
Inspect the transmission fluid: verify the level using the dipstick, and assess color and smell—dark or burnt-smelling fluid suggests internal clutch wear or overheating that may accompany solenoid issues.
Use a professional-grade scan tool to view live transmission data, including solenoid operation status, input and output shaft speeds, and line pressure readings, to confirm whether the solenoid responds correctly to commands.
Clear P0799 after your inspection, then drive the vehicle through a complete drive cycle that replicates the freeze frame conditions before checking whether the code returns.

Repair Options with Costs

Transmission fluid service (drain, fill, and filter replacement): $150–$350
Shift or pressure control solenoid replacement: $300–$800
Valve body repair or full replacement: $700–$1,500
Transmission rebuild or complete replacement: $2,500–$5,500

Prices reflect typical parts and labor at an independent shop in USD and may vary by vehicle and region.

Total Cost to Fix P0799

The actual repair expense hinges entirely on which component is responsible for the fault. In most straightforward cases, a transmission fluid service or solenoid replacement resolves the issue for $150 to $800. If the valve body requires attention, expect to pay $700 to $1,500. The most expensive scenario—a full transmission rebuild or replacement—can run $2,500 to $5,500. Always pursue accurate diagnosis before purchasing parts; the highest-cost repair is rarely the first place to look, and skipping cheaper troubleshooting steps often leads to unnecessary expense.

Can You Drive with P0799?

Use caution before driving any distance. If the transmission continues to shift predictably and no limp mode is active, short trips on lower-speed roads may be acceptable while you arrange a diagnosis. However, avoid highway driving, rapid acceleration, and heavy loads—continued operation with slipping gears or active fault codes accelerates internal wear and can transform a minor solenoid issue into a catastrophic transmission failure. Every mile driven under fault conditions potentially adds to your final repair bill.