P079F code meaning
Transmission Friction Element F Slip Detected
Powertrain system Generic code P07xx codes Check engine light
What P079F means
The 'friction element slip' codes monitor a clutch that is commanded locked in a power-split hybrid transmission: the module calculates its slip from electric motor, engine and output speeds (target 0 rpm) and flags slip above a threshold for a minimum time, with sufficient line pressure and clutch torque; from 2016 GM also flags a calculated friction energy threshold at once. The letter matches the manufacturer's clutch number. P079F concerns clutch 6. No manufacturer document available to us uses it – the documented hybrids (GM Two-Mode, Volt, Malibu Hybrid, CT6 plug-in, Chrysler Pacifica PHEV) have at most five monitored clutches. The description follows the family; clutch 6 would be the sixth friction element.
P079F at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor1 to 12 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P079F
- Check engine light or 'service hybrid system' message
- Limp mode with reduced power or restricted drive mode
- Slipping, engine speed rises without drive
- Jolt when the engine starts or stops
Common causes of P079F
- Most likelyClutch F plates worn or glazed
- PossibleToo little line pressure: low or aged fluid, filter, auxiliary oil pump or blocked pressure orifice
- PossiblePressure or shift valve of clutch F or valve body sticking
- Less likelyModule software (false setting)
- Less likelyFaulty speed signals (motor resolver, output)
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Transmission clutchesTransmission valve bodyAuxiliary transmission oil pumpHybrid control module
What each part of P079F means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 7 | Area: transmission. |
| 9F | The exact fault in that area. |
What to do next
- Note P079F and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P079F
What does P079F mean?
P079F means "Transmission Friction Element F Slip Detected". The 'friction element slip' codes monitor a clutch that is commanded locked in a power-split hybrid transmission: the module calculates its slip from electric motor, engine and output speeds (target 0 rpm) and flags slip above a threshold for a minimum time, with sufficient line pressure and clutch torque; from 2016 GM also flags a calculated friction energy threshold at once. It is a generic code, so it means the same on every make.
Is it safe to drive with P079F?
Drive gently and only to a workshop. With P079F the car can go into limp mode (reduced power) to protect itself.
Will P079F fail an emissions test?
Yes, it can. P079F is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P079F to fix?
Difficulty: hard. A typical repair takes 1 to 12 hours of work. This is a job for a workshop.
Will P079F clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.