OBD-II Trouble Code Technical Description
The code indicates that there is a detected slip in Transmission Friction Element A.
What does that mean?
This is a generic powertrain diagnostic trouble code (DTC) that is commonly found in OBD-II vehicles with automatic transmissions. This includes vehicles from various manufacturers such as Chevrolet, GMC, Toyota, VW, Ford, Honda, Dodge, Chrysler, etc. While the code is generic, the specific 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 complexity of the mechanical operation of an automatic transmission (A/T), which involves multiple friction elements. 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 consider the overall health of the automatic transmission and the condition of the Automatic Transmission Fluid (ATF) as the first step.
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, as even minor differences can cause indirect issues like this.
When the Engine Control Module (ECM) activates this P079A 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. It is advisable to seek appropriate help, as even professionals can make easily overlooked mistakes that can be costly.
In this case, the letter “A” may refer to a specific circuit/wire or a specific friction element within the transmission. Always refer to your service manual for specific locations, distinctions, and other specifications.
Code P079A is logged by the ECM when it detects slip in the internal “A” 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 P079A trouble code may include:
What are some of the common causes of the code?
Causes for this P079A friction element slip code may include:
What are some P079A 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
Most likely, when trying to find the connector/harness for this system, you will have to find a junction connector. There may be one “master” connector so make sure you are working with the correct one by referring to your manual. Make sure the connector itself is seated properly to ensure a good electrical connection. Where the connector is located on the A/T, it may be subject to vibrations that could cause connections to come loose or physically damage them. Not to mention, the possibility of ATF to saturate connectors and wires causing future or present issues.
Basic Step #3
It is always wise to be aware of the overall condition of your vehicle. Given the fact that, like in this case, other systems can directly affect other systems. Uneven tires, worn out suspension parts, incorrect wheels, all of these can and will cause issues in this system sand possibly others as well, so even things out, and you may rid of 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.
