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P0779 Pressure Control Solenoid B Intermittent

OBD-II Trouble Code Technical Description

Article by
John Ingalls
John Ingalls
Former Service Manager & Air Force Mechanic

Pressure Control Solenoid B Intermittent

What does that mean?

This is a generic transmission diagnostic trouble code (DTC) and typically applies to OBD-II vehicles equipped with an automatic transmission.

That may include but is not limited to vehicles from Ford, Mercury, Lincoln, Jaguar, Chevrolet, Toyota, Nissan, Allison/Duramax, Dodge, Jeep, Honda, Acura, etc. Although generic, the exact repair steps may vary depending on year, make, model and powertrain configuration.

When the P0779 OBD-II trouble code is set, the Powertrain Control Module (PCM) has detected a problem with the Transmission Pressure Control Solenoid "B". Most automatic transmissions incorporate at least three solenoids that are solenoid A, B and C. The trouble codes related to the "B" solenoid are codes P0775, P0776, P0777, P0778 and P0779. The code set is based on the specific malfunction that alerts the PCM and illuminates the Check Engine Light.

The purpose of the Transmission Pressure Control Solenoids is to control the pressure of the fluid for the proper operation of an automatic transmission. The PCM receives an electronic signal based on the pressure within the solenoids. An automatic transmission is controlled by bands and clutches that change gears by having fluid pressure in the right place at the right time. Based on the signals from associated devices monitoring the speed of the vehicle, the PCM controls the pressure solenoids to direct fluid at the appropriate pressure to various hydraulic circuits that change the transmission gear ratio at the correct time.

The code P0779 is set by the PCM when the Pressure Control Solenoid "B" is operating intermittently.

Example of a transmission pressure control solenoid:
P0779 Transmission Pressure Control Solenoid

What is the severity of this DTC?

The severity of this code normally starts as moderate, but it can progress to a more severe level rapidly when not corrected in a timely manner.

What are some of the symptoms of the code?

Symptoms of a P0779 trouble code may include:

What are some of the common causes of the code?

Causes for this P0779 transmission code may include:

What are some P0779 troubleshooting steps?

Prior to beginning the troubleshooting process for any malfunction you should research the Technical Service Bulletins (TSB's) for the specific vehicle by year, model and transmission. In some circumstances this can save a lot of time in the long run by pointing you in the right direction. You should also check the vehicle records to verify the last time that the filter and fluid was changed if possible.

Fluid & Wiring Inspections

The first step is to check the fluid level and examine the condition of the fluid for contamination. Prior to changing the fluid, you should check the vehicle records to verify the last time that the filter and fluid was changed.

A detailed visual inspection to check the condition of the wiring for obvious defects is next. Check the connectors and connections for security, corrosion and damaged pins. This should include all wiring and connectors to the transmission pressure control solenoids, the transmission pump and the PCM. Depending on the configuration, the transmission pump may be electrically driven or mechanical driven.

Advanced Steps

The advanced steps always become very vehicle specific and require the appropriate advanced equipment to perform accurately. These procedures require a digital multi meter and the specific technical references for the vehicle. You should obtain the specific troubleshooting guidelines for your vehicle prior to proceeding with the advanced steps. Voltage requirements may very based on the specific model of the vehicle. Fluid pressure requirements will also vary based on the transmission design and configuration.

Continuity Checks

Unless otherwise specified by the technical data, the normal readings for wiring and connections should be 0 ohms of resistance. Continuity checks should always be performed with the power removed from the circuit to avoid shorting the circuit and creating more damage. Resistance or no continuity is an indication of faulty wiring that is open or shorted and must be repaired or replaced.

What are some common repairs for this code?

Possible misdiagnosis may include:

Hopefully, the information in this article has been helpful to point you in the right direction to correct the problem with your pressure control solenoid trouble code. This article is strictly informational and the specific technical data and service bulletins for your vehicle should always take priority.

Related P0779 DTC Discussions

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