B3991

B3991 Ford engine fault code diagnosis, code meaning,symptoms and how to fix it.

B3991 Diagnosis

The BHM supplies battery power on this circuit when the key is in the RUN or CRANK positions. Troubleshoot for an open circuit fault.The BHM is detecting more than one smart switch with the same ID number present on the vehicle. The outputs controlled by the switch and the indicator in the switch are commanded FF.

The BHM drives the 5 cab overhead clearance and ID lamps from connector B5 pin C on circuit 46. All other marker and tail lamps are driven from BHM connector B1,K on circuit 23. This circuit connects to the CHM as an input at connector J3,P.

Ford B3991 Fault Code Meaning :

Ford B3991 Symptoms :

Ford B3991 Reasons :

How To Fix Ford B3991 Trouble Code ?

Which Ford cars have the code B3991?

  • B3991 Ford Aerostar
  • B3991 Ford Bronco
  • B3991 Ford C-Max
  • B3991 Ford C-Max Energi
  • B3991 Ford C-Max Hybrid
  • B3991 Ford Contour
  • B3991 Ford Crown Victoria
  • B3991 Ford EcoSport
  • B3991 Ford Econoline
  • B3991 Ford Edge
  • B3991 Ford Escape
  • B3991 Ford Escape Hybrid
  • B3991 Ford Escort
  • B3991 Ford Everest
  • B3991 Ford Excursion
  • B3991 Ford Expedition
  • B3991 Ford Explorer
  • B3991 Ford Explorer Sport Trac
  • B3991 Ford F-150
  • B3991 Ford F-250
  • B3991 Ford F-350
  • B3991 Ford Fiesta
  • B3991 Ford Flex
  • B3991 Ford Focus
  • B3991 Ford Focus Electric
  • B3991 Ford Freestar
  • B3991 Ford Freestyle
  • B3991 Ford Fusion
  • B3991 Ford Fusion Energi
  • B3991 Ford Fusion Hybrid
  • B3991 Ford Fusion Plug-In Hybrid
  • B3991 Ford GT
  • B3991 Ford Mustang
  • B3991 Ford Mustang Mach-E
  • B3991 Ford Mystique
  • B3991 Ford Probe
  • B3991 Ford Ranger
  • B3991 Ford Taurus
  • B3991 Ford Taurus X
  • B3991 Ford Tempo
  • B3991 Ford Thunderbird
  • B3991 Ford Transit
  • B3991 Ford Transit Connect
  • B3991 Ford Windstar

A code is a fault code and it indicates that something has gone wrong with your car's engine.

It can be caused by many different problems, including a faulty battery, a bad fuel pump, or even a cracked exhaust manifold.

You will need to diagnose the problem before you can fix it. The best way to do this is with an OBD scanner tool.

A scan tool will tell you what needs fixing and how much it will cost in order to fix that particular issue.