Shuts off suddenly while driving

Tiny
HGWK
  • MEMBER
  • 2015 FORD FOCUS
  • 2.0L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 115,000 MILES
No diagnostic codes but it will show the message on the screen "starting system fault" or sometimes "no key detected". Lights on the dash sometimes flicker. If you try to start the car again right away it won't crank over the lights on the dash sometimes will come on and sometimes they don't! Usually car will restart within 10-20 minutes sometimes right away! Fuses, relays have been checked, battery is good and voltage is normal, has new fuel pump, problem was present prior to the new fuel pump. I tried 2 different keys which one of them is new makes no difference, tried disconnecting the battery for few minutes usually makes no difference. Also noticed while the car is not wanting to start it will not let you access some of the menu options as "my key" for example. I'm not sure but I'm suspecting something with anti theft or the ignition lock?
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Wednesday, June 30th, 2021 AT 11:33 AM

1 Reply

Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

The idea that it reacts differently at different times leads me to believe it is something with a module or a bad connection.

Here is what I suggest starting with. Have the CAN-bus system scanned. CAN stands for controller area network. The vehicle has several modules/computers in it. They are all tied together via a few wires to help eliminate the need for giant wiring harnesses and weight. If you use a basic scan tool, they usually can't identify anything other than a powertrain code. However, there are other modules that may be storing diagnostic codes. By scanning the CAN, it will identify anything that is stored regardless of the module it's stored in.

Here is a quick video showing how it is done:

https://youtu.be/InIlnsjOVFA

I suspect it could be something related to the ignition switch since it isn't recognizing 2 different keys when this happens. Do me a favor. I want you to remove fuse 78 (pics 1and 2 below) and check to make sure it's tight and there is no corrosion. This fuse should be in the body control module under the dash (I believe the passenger side).

Also, carefully check the mega fuse 4 in the battery junction box (BJB).

Both of these fuses have to be good because the problem comes and goes. However, I want them checked because you mentioned sometimes you lose dash lights. Something could be causing a loss of connection such as corrosion, being loose, or partially blown.

If everything checks good, have the CAN scanned to see if there is anything stored. We may end up having to have the BCM reprogrammed. Also, make sure the battery terminals are clean and tight, free of corrosion.

Here is a link you may find helpful:

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Let me know what you find.

Joe

See pics below.
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Thursday, July 1st, 2021 AT 9:35 PM

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