P278A code meaning
Kick Down Switch Circuit
What P278A means
P278A is the general circuit fault of the kickdown switch, the contact at the end of accelerator pedal travel that asks the transmission for the lowest possible gear. No manufacturer documents P278A publicly. Many current cars no longer have an electrical switch: Mazda states for the 2024 CX-90 that its kickdown element only adds a felt detent and sends no signal, the pedal position sensor alone deciding. Where a real switch or message exists, the transmission control checks it; Eaton's Endurant HD gearbox logs fault 167 if the kickdown message from the pedal is missing or invalid for 5 s. CARB requires circuit monitoring for such inputs. P278B to P278E name the fault type more precisely. Without the signal, full-throttle downshifts may be weaker or later.
P278A 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 P278A
- No forced downshift at full throttle
- Reduced acceleration when overtaking
Common causes of P278A
- PossibleKickdown switch in or under the pedal defective
- PossibleWiring or connector of the pedal module damaged
- Less likelyKickdown message missing on the data bus (networked designs)
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Kickdown switchAccelerator pedalWiring harness
What each part of P278A 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. |
| 8A | The exact fault in that area. |
What to do next
- Note P278A 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 P278A
What does P278A mean?
P278A means "Kick Down Switch Circuit". P278A is the general circuit fault of the kickdown switch, the contact at the end of accelerator pedal travel that asks the transmission for the lowest possible gear. It is a generic code, so it means the same on every make.
Is it safe to drive with P278A?
P278A does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will P278A fail an emissions test?
P278A 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 P278A 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 P278A clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.