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

P05F9 Stop-Start Status Signal Circuit

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

A discrete stop-start status line tells the engine module (or another module) whether stop-start is active, inhibited or has just stopped the engine. On most current cars this status travels over CAN instead, so a hard-wired line and these codes are rare; no manufacturer document available to us uses P05F9–P05FB. CARB names stop-start as its example of an 'emissions neutral' reaction: a module that simply disables stop-start when a fault appears may report it without the check engine light, which is what Ford does for its stop-start codes. P05F9 is the general circuit fault or open line. The typical reaction is that stop-start is disabled; the driver-operated stop-start switch has its own codes.

Likely causes

Open status line or connector problem
Sending module without supply or faulty
Wrong software or variant coding (stop-start set without hardware)

Symptoms

  • Stop-start does not work
  • Stop-start indicator or message in the cluster
  • Check engine light only with some makers

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–300
Time0.5–2 h

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

Parts involved

stop start status linebody control moduleengine control module

Related codes

P05FAP05FBP05FFP0504

References: law.cornell.edu, fordservicecontent.com, patents.google.com.