P278C code meaning
Kick Down Switch Circuit Low
What P278C means
P278C is recorded when the kickdown switch line reads lower than the module allows. No manufacturer documents P278C publicly, and many modern pedals have no electrical kickdown contact at all, as Mazda notes for the 2024 CX-90. On designs with a wired switch the cause is usually the signal pulled to ground: insulation damaged where the harness passes the pedal bracket, a switch contact welded or shorted, or water from the footwell reaching the plug. Depending on the circuit logic the module may then read a permanent kickdown request or none at all. CARB demands such out-of-range checks for inputs. Unlike P278D the signal sits too low, unlike P278B it is not just implausible. Shift behaviour at full throttle becomes unreliable.
P278C at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyEasy, DIY possible
- Typical labor0.3 to 1.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P278C
- Kickdown always or never active, depending on circuit
- Unexpected downshifts or lack of downshift at full throttle
Common causes of P278C
- Most likelySignal wire shorted to ground at the pedal bracket
- PossibleSwitch contact welded or shorted
- Less likelyWater from the footwell in the connector
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Kickdown switchWiring harness
What each part of P278C means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 7 | Area: transmission. |
| 8C | The exact fault in that area. |
What to do next
- Note P278C 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 P278C
What does P278C mean?
P278C means "Kick Down Switch Circuit Low". P278C is recorded when the kickdown switch line reads lower than the module allows. It is a generic code, so it means the same on every make.
Is it safe to drive with P278C?
P278C does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will P278C fail an emissions test?
P278C is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is P278C to fix?
Difficulty: easy. A typical repair takes 0.3 to 1.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P278C clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.