P0798 OBD-II Trouble Code: Pressure Control Solenoid “C” Electrical

Our certified mechanics come to you · 12-month, 12,000-mile warranty

SCHEDULE P0798 DIAGNOSTIC Get a fair and transparent estimate upfront
Red-stars EXCELLENT RATING ON

Cost of diagnosing the P0798 code

P0798 is a diagnostic trouble code (DTC) for "Pressure Control Solenoid “C” Electrical". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.

Cars Estimate Credit towards follow-up repair Earliest Availability
Ford$20.00
Toyota$20.00
BMW$20.00
SCHEDULE P0798 DIAGNOSTIC Get a fair and transparent estimate upfront

A P0528 code indicates that the powertrain control module (PCM) has registered a problem related to an electronic pressure control solenoid or solenoid circuit.

What the P0798 Code Means

Computer controlled automatic transmissions actuate gear shifts and torque converter lockup via electronic pressure control solenoids. A P0798 code means that one of these solenoids is sending out readings that are out of parameters.

What causes a P0798 code?

  • Low transmission fluid level
  • Dirty or contaminated transmission fluid
  • Internal mechanical failures
  • Internal hydraulic passages blocked
  • Failed electronic pressure control solenoid
  • Failed PCM or transmission control module

What are the symptoms of a P0798 code?

  • Limp-in mode
  • Harsh shifts
  • Transmission slipping
  • Transmission overheating
  • Poor fuel economy
  • Failure of torque converter clutch to lock up or disengage
  • Disabled shifting – stuck in one gear
  • No detectable symptoms at all
  • Stored code and illuminated malfunction indicator lamp (MIL)

Other codes related to transmission slippage, gear ratios, torque converter clutch/lockup or shift solenoids may accompany this code.

How does a mechanic diagnose a P0798 code?

Ever since electronic automatic transmissions were introduced in the mid-1980s, vehicles have used a computerized control system that governs shifts based on information on vehicle speed, transmission output speed, engine load and engine/turbine speed. It determines shift points and the proper gear ratio for a given speed or engine load, optimizing engine performance and fuel economy.

The powertrain control module (PCM) uses this data to regulate transmission fluid pressure, via a high pressure pump (driven by the torque converter) and pressure control solenoids. The solenoids then govern the flow of fluid through the transmission’s internal hydraulic circuits. For a proper diagnosis, a technician will need a good quality scanner/code reader and a digital volt/ohmmeter (DVOM).

  • Any transmission diagnosis should start with an inspection of the transmission fluid on the dipstick. The fluid level should be within manufacturer’s recommendations and the fluid should be in good condition.

  • Fluid that smells burned is an indicator of transmission overheating, usually due to operation at a low fluid level. Internal mechanical failure may accompany burned fluid.

  • If fluid appears or smells burned, drop the transmission pan. Check for clutch material, metal shavings and other debris.

  • If debris is present in the transmission pan, a complete rebuild/fluid flush and new torque converter will likely be needed for the transmission to function properly.

  • If no debris is found in the pan, look closely for shorted or burned wiring or connectors in internal transmission wiring. Replace as needed. Most applications will require a full replacement of the internal transmission harness.

  • If the internal wiring, connectors and components all seem to be in good working order, connect the scanner to the diagnostic port and record any stored trouble codes. Freeze-frame the data.

  • Clear the codes and test drive the vehicle to see if codes return.

  • If codes don’t return, the problem may be an intermittent condition which may need to be allowed to worsen and return before a proper diagnosis can be made.

  • If transmission fluid is low, add fluid and find the source of a leak. Clean the bottom of the transmission, pan and crossmember using brake cleaner, then spray foot powder on the entire area to make it easier to track down the source and path of a leak.

  • If, after filling the transmission with the proper fluid, the code doesn’t return, it may have been caused by a low fluid level.

  • If the code returns and the transmission shows signs of slippage or delayed engagement, move on and check pump pressure using a manual pressure gauge.

  • Locate the appropriate port on the transmission housing and thread the end of the gauge to the port to record pump pressure. Compare your pump pressure readings with factory specs and repair accordingly.

  • Causes of low pump pressure can include a failed pump, clogged internal hydraulic passages, failed electronic pressure regulator or failed shift solenoids. Replacement of the pump will mean transmission removal and partial teardown.

  • If the transmission seems to operate normally but the code immediately returns, look for reference voltage and ground signals at the suspected pressure control solenoid.

  • Disconnect any related control modules from the circuit before checking circuit resistance, to ensure against damage.

  • Repair/replace any related systems circuits/connectors as needed. Retest the system to ensure that resistance and continuity are in line with factory specs. A manufacturer’s wiring diagram will be needed.

  • If all circuits are intact and resistance and continuity are within factory specs, connect the scanner and attempt to manually engage the electronic pressure control solenoid. If the solenoid will not actuate manually, replace the solenoid and retest the system.

  • If the control solenoid is good and all circuits are within factory spec, look for a defective high pressure pump, torque converter or PCM. Remember that PCM failure is rare.

Common mistakes while diagnosing P0798 code

In these instances, the electronic pressure control solenoid or wiring problems are often overlooked, with technicians going straight to the high pressure pump and replacing it in error.

How serious is a P0798 code?

A P0798 code can result in limp-in mode or a transmission that will not shift out of a given gear, and can lead to further problems.

What repairs can fix a P0798 code?

Addition comments for consideration for P0798 code

The parameters for setting a P0798 code can vary considerably from one manufacturer or even one model to another. Make sure you understand your vehicle’s make/model specs before going any farther.

Need help with a P0798 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6220.

trouble codes
P0798
Check Engine Light

Fast and easy Check Engine Light is on Inspection service at your home or office.

SCHEDULE P0798 DIAGNOSTIC
Get a fair and transparent estimate upfront

Recent Check Engine Light is on Inspection reviews

Excellent Rating


YourMechanic Check Engine Light is on Inspection Service

Average Rating

4.8/5

Number of Reviews

4,829

Rating Summary
4,442
187
48
28
124
4,442
187
48
28
124

Walter

44 years of experience
64 reviews
Walter
44 years of experience
Jeep Grand Cherokee - Check Engine Light is on - Tulsa, Oklahoma
Went above and beyond my expectations, as i was very nervous about this type of service! But to my surprise, I am absolutely satisfied with the service ! Would recommend 100X to all i know! Thanks for the care and information and time you put in to my qoute and truck@

Keith

16 years of experience
279 reviews
Keith
16 years of experience
BMW 535i xDrive - Check Engine Light is on - Kissimmee, Florida
Very personable, knowledgeable person, who provided information on my car that I was not aware of. The overall experience was great and I would definitely refer this company to my family and friends.

Luis

13 years of experience
20 reviews
Luis
13 years of experience
Audi A3 - Check Engine Light is on - Van Nuys, California
Luis was awesome. Very knowledgeable and a down to earth person. Would highly recommend and plan on using him in the future for any repair that I need!

Joel

19 years of experience
742 reviews
Joel
19 years of experience
Acura RL - Check Engine Light is on - Jacksonville, Florida
very knowledgeable and precise. able to fix electrical issues in my car. Right on time for the appointment.

More related articles

P2705 OBD-II Trouble Code: Transmission Friction Element F Apply Time Range/Performance
P2705 means there is a malfunction in the transmissions friction elements due to failing transmission components, low fluid level or electrical issues
P0346 OBD-II Trouble Code: Camshaft Position Sensor A Circuit Range/Performance (Bank 2)
P0346 P0346 code definition The appearance of the P0346 code indicates that the PCM has detected an incorrect voltage or waveform reading from the engine bank 2 camshaft sensor A camshaft position sensor circuit. What the P0346 code means The...
P0330 OBD-II Trouble Code: Knock Sensor 2 Circuit Malfunction (Bank 2)
P0330 code definition P0330 is a general OBD-II trouble code that is indicating a malfunction in the knock sensor circuit 2. Note:...

Related questions

Car stopped, steering wheel stuck, check engine light orange

It sounds like you may have a failing alternator. The alternator is responsible for running the electrical system of your vehicle while the engine is running as well as keeping the battery fully charged. If the alternator fails, this can...

What else can it be besides the fuel pump, relay, and fuel filter if my tahoe putts

The check engine light means the ECM has stored a code in memory. The code may be indicating the problem causing the problem you are having. The problem sounds like you are having an issue with the fuel control, such...

Check engine light code for a misfire

Hi there. A misfire code is set when the engine computer sees a slow down in one or more pistons due to incomplete combustion. This can either be from a lean or rich condition. The task at hand is to...

How can we help?

Our service team is available 7 days a week, Monday - Friday from 6 AM to 5 PM PST, Saturday - Sunday 7 AM - 4 PM PST.

1-800-701-6230 · hi@yourmechanic.com