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

Our certified mechanics come to you · 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 for $154.99 . Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $50.0 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 $154.99 $50.0
Toyota $154.99 $50.0
BMW $164.99 $50.0

*Estimates may vary by market

SCHEDULE P0798 DIAGNOSTIC Get a fair and transparent estimate upfront

A P0538 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 1-800-701-6230.

Check Engine Light
trouble codes
P0798

No more waiting rooms! Our mechanics will come to you to diagnose and fix the P0798 code.

SCHEDULE P0798 DIAGNOSTIC
Get a $50 credit for the follow-up repair

Recent Check Engine Light is on Inspection reviews

Excellent Rating

(8600)

Rating Summary
8017
273
65
46
199
8017
273
65
46
199
 at YourMechanic

Brandon

9 years of experience
133 reviews
Brandon
9 years of experience
Ford Escort L4-2.0L - Check Engine Light is on - Nashville, Tennessee
Brandon showed up ahead of schedule, was very personable and diagnosed my problems. He also scheduled my next appointments which will be with him.
 at YourMechanic

William

23 years of experience
33 reviews
William
23 years of experience
Lexus IS250 V6-2.5L - Check Engine Light is on - Mableton, Georgia
Arrived early which was great. William was courteous, and attentive to the issue. Even though it took several attempts I'm so happy he was determined to fix it and he did!
 at YourMechanic

Dan

40 years of experience
1080 reviews
Dan
40 years of experience
Plymouth Grand Voyager - Check Engine Light is on - Lawrenceville, Georgia
Mr. Dan Barber was quite patient, courteous and quite knowledgeable. From my observation, Mr. Barber appears to be quite professional.
 at YourMechanic

Christopher

9 years of experience
120 reviews
Christopher
9 years of experience
Ford Fiesta L4-1.6L - Check Engine Light is on - Smyrna, Georgia
Chris communicated with us each step of the way up until his arrival. He listened well, was knowledgeable, and was prepared. He took the time to diagnose the problem, explained the what, why and how and provided a solution. I would definitely recommend him and will use him again.


More related articles

P0593 OBD-II Trouble Code: Cruise Control Multi-Function Input “B” Circuit High
P0593 means an error with the cruise control multi-function input B circuit, often caused by a interior spill that damages the cruise control switch.
P0698 OBD-II Trouble Code: Sensor Reference Voltage “C” Circuit Low
P0698 means there is an irregular voltage level or connectivity problem relating to the electrical circuitry due to faulty wiring or connections.
B1939 OBD-II Trouble Code: Air Bag Passenger Pressure Switch Circuit Short to Ground
B1939 means there is an issue with the air bag pressure switch on the passenger side, likely due to a malfunction in the switch or module.

Related questions

CEL purge valve manifold
Hello there, thank you for asking about your 2011 Mercedes-Benz C63 AMG. If you are suspicious, you may want to hire another facility for a second opinion. Each time the Check Engine Light was illuminated, there's a good chance the...
Misfire caused bad o2 sensor?
As you may know the oxygen sensors which are part of your emissions system read exhaust gases to determine whether or not the appropriate amount of oxygen is present in the exhaust. Based upon this reading, this information is relayed...
Saturn vue 2005 check engine light most of the time P0172 errors.
P0172 means the fuel system is too rich; rich beyond the ability of the closed loop system to compensate. It might be a vacuum leak, a mass air flow sensor, or a fuel pressure regulator problem. At that age it...

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 (855) 347-2779 · hi@yourmechanic.com