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

P05BD Stop-Start Mode Switch Circuit Range/Performance

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. P05BD means the switch signal is valid but implausible. On the 2025 Ram 1500 Stellantis sets it when the engine module receives 120 presses of the stop-start button within 2 minutes over CAN – a sticking or bouncing button or a flood of messages. The first fix is an engine module software update, not parts; Stellantis warns not to replace the ignition switch for it.

Likely causes

Engine module software (Stellantis: fixed by update)
Sticking or bouncing stop-start button in the shifter module
Very frequent pressing by occupants
Shifter module faulty

Symptoms

  • Usually no noticeable symptoms
  • Stop-start button not reacting or status jumping
  • Code stored in the engine module

Repair estimate

DifficultyEasyWorkshop job
Parts and labour€0–250
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

P05BCP05BEP05BFP05C8

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