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Error Code P079F is defined as Transmission Friction Element “F” Slip Detected. This is a generic trouble code, meaning it applies to all vehicles with the OBD-II system, especially those made from 1996 up to present and equipped with automatic transmission. Specifications on the definition and steps for repairs may vary depending on the model and make of the vehicle.
This includes vehicles from, but not limited to, Chrysler, Chevrolet, Dodge, Ford, GMC, Honda, Volkswagen, Toyota, etc. Specifications on the definition, troubleshooting, and repairs, of course, vary from one make, model, and powertrain configuration.
When this Error Code P079F takes place, the PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes) has proactively been monitoring and adjusting other systems and sensors to ensure the right self-diagnosis. Thus, you need to address this problem as soon as possible to prevent further potential issues. It is possible that it can be a quick fix. However, the problem can also be as complex as internal electrical malfunction (open, short, water intrusion). Make sure you have your vehicle thoroughly checked by professionals, as even pros can overlook, and mistakes can cost thousands of dollars.
Internal friction problems in automatic vehicles usually leads to erratic driving conditions as far as shift timing, torque output, etc. Inflated tires, abnormally paired tires, etc., can cause internal slippage due to the unsymmetrical circumstances. Thus, it is important to consider the functionality of the drivetrain when troubleshooting any faults. When you have installed a new tire latterly, make sure you check the sidewall to verify. Minor differences can cause indirect problems.
Symptoms and causes of this error code vary on a lot of things, but it’s important to consider the overall health of the A/T (automatic transmission) and the ATF (automatic transmission fluid).
The “F” in the description refers to a few different possible distinctions. It may be a specific circuit or wire, or a friction element within the transmission. Thus, when this code is stored, that means the PCM has detected an internal “F” friction element inside the transmission.
- Transmission slippage
- Abnormal shift patterns
- Erratic shifting
- Uneven handling
- Harsh shifting
- Low torque
- Abnormal power output
- Low tire air pressure
- Low automatic transmission fluid
- Dirty ATF
- Worn friction element (internal)
- Wiring problem (short, open, chafed, burnt)
- Uneven tires
- Issues that cause uneven rotational speed/circumference (low tire pressure, stuck brake, etc.)
- TCM or PCM issue
- Water damage to the module or harness
How to Check
As with most error codes, the first step for effective troubleshooting for this code is to check with the Technical Service Bulletins (TSB) for the known issues of the specific vehicle.
Most advanced steps for diagnostics are vehicle specific, which may require the use of advanced equipment and expertise. Here are some basic steps for the diagnosis of this error code.
At this point, it is crucial that you follow the basic steps for the maintenance of the transmission.
This means you start at the fluid. Check the ATF, it must be clean, free of debris, and should have followed proper maintenance schedules to avoid faults like this in the future. If you’re unable to remember the last time the vehicle’s transmission has been serviced (filter, fluid, and gasket replacement), it’s best to perform this before continuing your diagnosis.
In some cases, debris in the oil trapped internally is the cause of the problem.
Make sure you use the right ATF for your specific vehicle make and model.
You will need to find a junction connector when looking for the connector/harness for this system. In many cases, there may be one “master” connector, so make sure you refer to the manual to know you’re working with the right one. Make sure the connector itself is seated properly to ensure there is 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 damage them physically. Not to mention the possibility that the ATF can saturate the connectors and wires causing future or present issues.
It is always good to be aware of the overall condition of the vehicle. Other symptoms may affect other systems. Uneven tires, incorrect wheels, worn out suspension parts, etc., all can cause problems with the system, and possibly others.
How to Fix
Common repairs for this code include:
- Properly add air to car tires
- Replacement or refilling of ATF
- Repair or replacement of wiring issue
- Use even tires
- Use correct wheels
- Replacement of worn-out suspension parts
- Repair or replacement of damaged module or harness
This code is a serious problem and must never be left unattended, especially when the vehicle is driven daily.