OBD-II Trouble Code Technical Description
The code indicates that there is a slip detected in the transmission friction element B.
What does that mean?
This is a generic powertrain diagnostic trouble code (DTC) that is applicable to OBD-II vehicles with automatic transmissions. This includes vehicles from various manufacturers such as Chevrolet, GMC, Toyota, VW, Ford, Honda, Dodge, Chrysler, etc. The repair steps may vary depending on the year, make, model, and powertrain configuration of the vehicle.
The description of “transmission friction element” is quite vague considering the multiple friction elements involved in the mechanical operation of an automatic transmission (A/T). It is important to note that manual transmissions also use similar friction materials, such as clutches.
In this case, it is likely that we are referring to an A/T. The symptoms and causes can vary significantly depending on various factors. However, it is crucial to first consider the overall health of the automatic transmission and the condition of the Automatic Transmission Fluid (ATF).
Problems with the internal friction materials in the A/T can lead to erratic driving conditions, including issues with shift timing, torque output, and other consequences. Factors such as abnormally paired tires or inadequately inflated tires can cause internal slippage due to their unsymmetrical circumstances. Therefore, it is important to consider the functionality of the drivetrain and troubleshoot any faults accordingly. If you have recently installed a used tire, make sure it is the same size as the others and check the tire’s sidewall for verification. Minor differences in tire size can indirectly cause issues like this.
When the Engine Control Module (ECM) activates this P079B code and related codes, it proactively monitors and adjusts other sensors and systems to ensure proper self-diagnosis. Therefore, it is crucial to address this issue before it potentially leads to further problems. While it may be a simple fix, it could also indicate a complex internal electrical malfunction, such as a short, open circuit, or water intrusion. Seek appropriate help to avoid costly mistakes.
The letter “B” in this case may refer to a specific circuit/wire or a specific friction element within the transmission. Always refer to the service manual for specific locations, distinctions, and other specifications.
Code P079B is logged by the ECM when it detects slip in the internal “B” friction element inside the transmission.
What is the severity of this DTC?
As mentioned earlier, it is not advisable to leave this issue unattended, especially if you are actively using the vehicle with the fault(s) present. It is important to prioritize addressing this issue, especially if you rely on the vehicle for daily transportation.
Photo and cutaway of an automatic transmission:
What are some of the symptoms of the code?
Symptoms of a P079B trouble code may include:
What are some of the common causes of the code?
Causes for this P079B friction element slip code may include:
What are some P079B troubleshooting steps?
The first step in the troubleshooting process for any malfunction is to research the Technical Service Bulletins for known issues with the specific vehicle.
Advanced diagnostic steps become very vehicle specific and may require the appropriate advanced equipment and knowledge to perform accurately. We include basic steps below but refer to a vehicle year/make/model/powertrain specific repair guide for specific steps for your vehicle.
Basic Step #1
It is imperative that you follow basic maintenance procedures accordingly at this point, as far as the transmission’s health goes, start at the fluid. Your ATF (Automatic Transmission fluid) needs to be clean, free of debris and also, proper maintenance schedules have to be followed to avoid more faults like this in the future. If you don’t remember the last transmission has been serviced (i.e. filter+fluid+gasket), it’s a good idea to perform this before continuing. Who knows there may be a bit of debris in your oil that is trapped internally. It may only take a simple service, so make sure you are aware of the last A/T service you have done.
NOTE: Ensure you are using the correct ATF for your specific make and model.
Basic Step #2
When trying to find the connector/harness for this system, you will most likely have to locate a junction connector. There may be one “master” connector, so ensure that you are working with the correct one by referring to your manual. Make sure the connector itself is properly seated to ensure a good electrical connection. The location of the connector on the A/T may subject it to vibrations that could cause loose connections or physical damage. Additionally, there is a possibility of ATF saturating connectors and wires, leading to present or future issues.
Basic Step #3
It is always wise to be aware of the overall condition of your vehicle. Other systems can directly affect the transmission and vice versa. Uneven tires, worn-out suspension parts, and incorrect wheels can cause issues in this system and possibly others as well. Therefore, it is important to ensure everything is balanced to potentially resolve this code.
This article is strictly for information purposes only, and the technical data and service bulletins for your specific vehicle should always take precedence.
