Powertrain, generic · Transmission
P077F Reverse 2 Incorrect Ratio
Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible
P077F checks the ratio in a second reverse gear: input speed divided by output speed lies outside the tolerance band around the target ratio – a slipping clutch, a wrong gear or a sensor fault. Only transmissions with two reverse ratios need it, such as Mercedes' 7G-Tronic (−3.42 and −2.23, with the second reverse kept in limp mode) and its 5G-Tronic predecessor; GM's 9- and 10-speeds, Ford's 10R and ZF's 8HP have one. No manufacturer document available to us uses this code; the check works like the other ratio codes such as P0736.
Likely causes
Slipping clutch or brake in the second reverse power path
Fluid level low or fluid worn
Solenoid or pressure regulator sticking
Faulty input or output speed sensor
Symptoms
- Reverse slips or engages late
- Limp mode
- Transmission warning or check engine light
Repair estimate
DifficultyHardWorkshop job
Parts and labour€200–3,500
Time1–12 h
Typical range across vehicles; the real cost depends on what the testing finds.
Parts involved
transmission clutchestransmission valve bodytransmission fluidtransmission control module
Related codes
References: en.wikipedia.org, law.cornell.edu, newtonnet.co.uk.