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

P05BC Stop-Start Mode Switch Circuit/Open

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. P05BC means the switch circuit is open. No manufacturer document available to us uses this code; Stellantis documents only its sibling P05BD. Typical are a connector left off after console or dashboard work or an open switch contact.

Likely causes

Open circuit in switch, connector or wire
Switch faulty (contact or resistor ladder)
Connector not refitted after console or dashboard work
Reading module or software

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

P05BDP05BEP05BFP05C7P057F

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