Powertrain, generic (extended)

P278D Kick Down Switch Circuit High

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

P278D means the kickdown switch circuit shows a voltage above its permitted maximum. No manufacturer documents P278D publicly. With the usual pull-up input this is the reading of an interrupted line: the pedal module unplugged after a repair, a broken wire at the hinge of a floor-mounted pedal, or a missing ground at the switch. A short to battery voltage produces the same picture but is rarer. For networked pedals the comparable case is a message that is missing or flagged as invalid, as Eaton describes for the kickdown signal of its Endurant HD gearbox (fault 167, 5 s). CARB requires out-of-range checks on such inputs. P278C is the low-voltage twin. Kickdown requests are lost until the circuit is restored.

Likely causes

Open signal or ground wire, pedal module unplugged
Wire broken by pedal movement
Signal wire shorted to battery voltage

Symptoms

  • No kickdown at full throttle
  • Slower acceleration from speed

Repair estimate

DifficultyEasyDIY possible
Parts and labour€30–400
Time0.3–1.5 h

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

Parts involved

kickdown switchwiring harness

Related codes

P278AP278BP278CP278E

References: law.cornell.edu, productinfo.serviceranger4.com.