P077F code meaning
Reverse 2 Incorrect Ratio
Powertrain system Generic code P07xx codes Check engine light
What P077F means
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.
P077F 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 P077F
- Reverse slips or engages late
- Limp mode
- Transmission warning or check engine light
Common causes of P077F
- Most likelySlipping clutch or brake in the second reverse power path
- PossibleFluid level low or fluid worn
- PossibleSolenoid or pressure regulator sticking
- Less likelyFaulty input or output speed sensor
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Transmission clutchesTransmission valve bodyTransmission fluidTransmission control module
What each part of P077F 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. |
| 7F | The exact fault in that area. |
What to do next
- Note P077F 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 P077F
What does P077F mean?
P077F means "Reverse 2 Incorrect Ratio". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P077F?
Drive gently and only to a workshop. With P077F the car can go into limp mode (reduced power) to protect itself.
Will P077F fail an emissions test?
Yes, it can. P077F 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 P077F to fix?
Difficulty: hard. A typical repair takes 1 to 12 hours of work. This is a job for a workshop.
Will P077F clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.