Powertrain, generic · Vehicle speed, idle control and auxiliary inputs

P05BF Stop-Start Mode Switch Circuit High

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

The stop-start off switch lets the driver disable automatic engine stop for the current drive. It is read directly or via another module over CAN – on Stellantis' 2025 Ram 1500 it sits in the electronic shifter module. CARB names a stop-start diagnosis as its example of an emission-neutral diagnosis, so no warning lamp is required; stop-start is usually just disabled. P05BF means the switch circuit voltage is too high – a short to positive or, with a pull-up, a missing switch ground. No manufacturer document available to us uses this code.

Likely causes

Signal line shorted to positive
Switch ground open (signal pulled up)
Switch faulty
Module input

Symptoms

  • Stop-start cannot be switched off or stays disabled
  • Switch indicator not working
  • Usually no check engine light

Repair estimate

DifficultyEasyDIY possible
Parts and labour€30–200
Time0.3–1.5 h

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

Parts involved

stop start switchswitch wiringengine control module

Related codes

P05BCP05BDP05BEP05CA

References: static.nhtsa.gov, vehicleservicepros.com, law.cornell.edu.