Powertrain, generic · Transmission

P079F Transmission Friction Element F Slip Detected

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

Clutch F plates worn or glazed
Too little line pressure: low or aged fluid, filter, auxiliary oil pump or blocked pressure orifice
Pressure or shift valve of clutch F or valve body sticking
Module software (false setting)
Faulty speed signals (motor resolver, output)

Symptoms

  • 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

Repair estimate

DifficultyHardWorkshop job
Parts and labour€150–4,500
Time1–12 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

transmission clutchestransmission valve bodyauxiliary transmission oil pumphybrid control module

Related codes

P07ACP07ADP2705P079AP0730

References: law.cornell.edu, patents.google.com, gsi.ext.gm.com.