OBD Codes
Your OBD-II Trouble Codes Repair Site

P079A Transmission Friction Element A Slip Detected

OBD-II Trouble Code Technical Description

Article by
Patrick Cameron
Patrick Cameron
Red Seal Certified Technician

Transmission Friction Element A Slip Detected

What does that mean?

This is a generic powertrain diagnostic trouble code (DTC) and typically applies to OBD-II vehicles that have an automatic transmission. That may include but is not limited to vehicles from Chevrolet, GMC, Toyota, VW, Ford, Honda, Dodge, Chrysler, etc. Although generic, the exact repair steps may vary depending on year, make, model and powertrain configuration.

Transmission friction element. Pretty vague description given the fact that there are numerous friction elements involved when you consider the mechanical operation of an automatic transmission (A/T). Not to mention manual transmissions also use similar friction materials (i.e. clutch).

In this case, I suspect we are referring to an A/T. The symptoms and causes vary significantly depending on many things but it is important to note, the first thing to consider is the overall health of the automatic transmission and especially your ATF (Automatic Transmission Fluid).

Problems with internal friction materials in the A/T most likely will cause erratic driving conditions as far as shift timing, torque output, among countless other consequences to this fault are concerned. Abnormally paired tires, inadequately inflated tires, things of this nature tend to cause internal slippage given it's unsymmetrical circumstances. That being said, keep this in mind when considering the drivetrain's functionality and troubleshooting any faults. Install a used tire lately? Same size? Check the tire’s sidewall to verify this. Sometimes, minor differences can cause indirect issues such as this.

Typically, when the ECM (Engine Control Module) activates this P079A code and related ones, it has proactively been monitoring and adjusting other sensors and systems in order to ensure proper self-diagnosis. So, rest assured, you need to address this before your daily driving needs consequently cause further potential issues. This may be a simple fix, definitely possible. That said, it may also be a complex internal electrical malfunction (i.e. short, open, water intrusion). Make sure to acquire help accordingly here, even pros make easily overlooked mistakes that costs thousands, speaking from experience here.

The letter in this case, "A", may refer to a few different possible distinction. You may be dealing with a specific circuit/wire or you may be dealing with a specific friction element within the transmission. Having said all that, always refer to your service manual for specific locations, distinctions, and other such 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 explained earlier, this isn't something that I would leave unattended, especially if you are actively using the vehicle with said fault(s) present. You should definitely prioritize this. Well, if driving your vehicle is a necessity, daily.

Photo and cutaway of an automatic transmission:
P079A 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.

Related P079A DTC Discussions

Need more help with a P079A code?

If you still need help regarding the P079A trouble code, please post your question in our FREE car repair forums.

NOTE: This information is presented for information purposes only. It is not intended as repair advice and we are not responsible for any actions you take on any vehicle. All information on this site is copyright protected.