P0798 — Pressure Control Solenoid C Electrical

OBD2 code P0798 flags a problem with the automatic transmission control (pressure control solenoid c electrical). Short, gentle driving to a shop is usually possible. Common culprits: internal mechanical wear (clutches, torque converter), failed shift or pressure control solenoid, wiring or connector faults in the valve body harness.

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 P0798 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 P0798 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for P0798 (parts and labor, USD, independent shop rates): Transmission rebuild or replacement: $2,500–$5,500; Replace a shift solenoid: $300–$800; Valve body repair or replacement: $700–$1,500; Transmission fluid service: $150–$350. Overall, fixing P0798 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

Is it safe to drive with P0798?

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 much does it cost to fix P0798?

Transmission rebuild or replacement — $2,500–$5,500; Replace a shift solenoid — $300–$800; Valve body repair or replacement — $700–$1,500; 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.

What is the most common cause of P0798?

The most common causes are: internal mechanical wear (clutches, torque converter), failed shift or pressure control solenoid, wiring or connector faults in the valve body harness.

Will P0798 clear itself?

Sometimes P0798 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 are the symptoms of P0798?

Drivers most often notice: no movement in severe cases, shuddering at highway speed, Check Engine or transmission warning light on, harsh or delayed shifting.

When your vehicle's engine control module detects a problem with the electrical circuit controlling hydraulic pressure inside an automatic transmission, it logs code P0798. This specific fault points to the pressure control solenoid designated as solenoid C. The powertrain control module continuously monitors the output of that solenoid against expected values; when the signal falls outside acceptable parameters for a sustained period, the system triggers P0798.

Automatic transmissions rely on precisely modulated hydraulic pressure to engage and release clutches and bands that create gear changes. Solenoid C is one of several electronically controlled valves that manage this fluid pressure. If the control module cannot achieve the commanded pressure or detects an open/short circuit condition, the transmission may default to a protective mode. That protective mode is why this code can produce noticeable drivability problems — the ECU essentially overrides normal shifting logic to prevent further damage.

Technicians refer to this as a Type A electrical fault in manufacturer service literature. To set P0798, the module typically requires multiple ignition cycles with the same condition present before illuminating the Check Engine light. The stored freeze frame data captures sensor readings at the exact moment the failure occurred, giving you a diagnostic starting point that often reveals whether the problem is temperature-related or occurs under specific load conditions.

Common Symptoms

Transmission refuses to shift into gear, leaving the vehicle immobile in serious cases
Noticeable shudder or vibration felt at highway cruising speeds
Dashboard warning light for the Check Engine or transmission indicator
Harsh engagements when changing gears or delayed response during shifts
Slippage where the engine revs higher without corresponding acceleration

Possible Causes

Worn or scored valve body channels restricting fluid flow
Insufficient or contaminated transmission fluid reducing hydraulic efficiency
Faulty pressure control solenoid C itself
Damaged wiring harness or corroded connectors at the transmission harness
Malfunctioning transmission input/output speed sensors affecting closed-loop control
Internal wear inside the transmission causing abnormal pressure demands

Diagnostic Steps

Hook up a quality OBD2 scanner and verify that P0798 is an active or pending code. Record all freeze frame data before clearing anything — these parameters tell you engine speed, vehicle load, coolant temperature, and road speed when the fault first appeared.
Look for any accompanying diagnostic codes. Related transmission or solenoid codes frequently expose the root cause faster than focusing on P0798 alone. Also research whether your specific make and model has a factory TSB addressing this code.
Perform a thorough visual inspection of the transmission electrical harness. Check for frayed wires near the transmission case, moisture intrusion at connectors, and any signs of previous repair work that may have damaged insulation.
Assess transmission fluid condition by checking color and smell. Black or burnt-smelling fluid suggests clutches or bands are wearing, which would explain abnormal pressure demands triggering P0798.
Use a transmission-capable scanner to view live solenoid operation, input speed sensor signals, and output speed sensor readings. Compare actual values against factory specifications while someone monitors the scanner during a test drive.
After addressing any obvious findings, clear the code and drive the vehicle through conditions matching the freeze frame data. If P0798 reappears, the fault is confirmed and component-level testing is next.

Repair Options and Costs

The appropriate repair depends entirely on what your diagnosis reveals. Here are typical scenarios with typical price ranges at independent shops:

Full transmission rebuild or replacement typically runs $2,500 to $5,500 including parts and labor
Replacement of a single pressure control solenoid generally costs $300 to $800
Valve body repair or complete unit replacement usually falls between $700 and $1,500
Transmission fluid and filter service with pan removal and gasket replacement costs $150 to $350

Total Repair Cost

Expect to pay between $150 and $5,500 to resolve code P0798. The wide range reflects how different underlying causes produce identical codes. A simple fluid service might clear the issue for under $200, while a failed solenoid requiring valve body access could approach $1,500. Complete transmission overhaul or replacement sits at the high end. Getting an accurate diagnosis before purchasing parts almost always saves money — the worst-case scenario is rarely the correct first step.

Driving Safety Verdict

Severity Level: Caution. If your transmission still completes shifts without slippage and the vehicle remains drivable, short trips to a repair facility are acceptable. However, continued operation with P0798 active risks entering limp-home mode or causing internal transmission damage that transforms a $500 fix into a $4,000 one. Have this code investigated promptly.