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So I had the exact issue you describe happen to my 2015 Focus ST.
In the end (fingers crossed) it ended up being a hairline crack in the 50A fuse going to the BCM. This fuse is located in the BJB just in front of the positive terminal on the battery box. Yellow wire with a green stripe.
found it would make a circuit and then sometimes loose the circuit.
My mirror lights were flashing like yours. My car alarm would go off. My car would recognize my key fob etc.
What a pain.
Nice to hear you got an edge ST.
I'm having the exact same issue! So nice to hear there are others as well and I'm not alone on this. I have a 2018 focus st base package, and here is my issue currently, and here is what I have found so far.

When I first bought the car used, I was driving it home and suddenly the throttle cuts, car sputters a little, and dies. I pull off to the side of the road with my head racing. Couple of strange things I noticed: 1. the front and rear right headlight and taillight were no longer on, 2. it was saying no key detected, but the battery in the fob was fine, and the secondary start method was not working either, telling me it's not the key, but the sensor in my car, and later findings showed it simply wasn't getting electricity.
I decide to wiggle the battery because yk, why not, I didnt want to have to pay several hundred to get it towed, and I had an interview for a job in the morning so I needed to get home and I was going to try everything I could.
I pulled on the main red battery terminal connector, and slid the battery forward, and i heard a slight beep like something finally connected. Now all the lights are on, and my key fob unlocks the doors and is being detected by my car. I hop in, and start driving, and after less then a minute, it shuts off again. I jump out of the car, pop the hood. pull the battery forward, hear the same beep, the lights are all on now and the key is now being detected. I drive the car several hours the rest of the way home.
Throughout the next couple weeks the issue continues, and I can re-create it upon hitting the acceleration which slides the battery back, killing the engine. I've checked all battery terminals, they're tight, and everything seems to work perfectly fine.
Recently, its been getting worse, and becoming more and more difficult to get started until last night, I can no longer get it to start. I decided to get precise and try to narrow down where the issue is occuring. I found after several hours of playing around with it that the plate in front of the battery where the main red battery connector goes to; if i move it less than a half inch the light comes on, but as soon as I release, they go back off and not key detected. I checked all connections and everything seems tight, and there is no corrosion. My mind is blown that I have it narrowed down to a specific small area, and still cannot find the issue, so my guess is the fuse like you are saying has a hairline crack. Did you ever get this solved?

I would absolutely love any feedback I can get from anyone, please dont tell me that it's a loose connection or a corroded battery terminal though, I've checked it all. It's something a little more precise.
 

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It was a crack in the fuse.
When your car dies....
Remove the airbox.
Remove the cover to expose the fuses on the front of the battery box.
With a DCVolt meter check the voltage on the bottom side of each fuse to ground.
Mine was The Body control module fuse. Last one on the right. a 50A fuse.
I saw only 2.5VDC getting through it not the 12.4VDC it should be with just the key on.
 

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Read this Post.
schematics from SSgtjrobertson helped huge.
 
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I just sent them the link
 
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You are a good man.
 

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Yeah, Don't let that **** get around :p
 
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It was a crack in the fuse.
When your car dies....
Remove the airbox.
Remove the cover to expose the fuses on the front of the battery box.
With a DCVolt meter check the voltage on the bottom side of each fuse to ground.
Mine was The Body control module fuse. Last one on the right. a 50A fuse.
I saw only 2.5VDC getting through it not the 12.4VDC it should be with just the key on.
Thank you so much for confirming this! It was the last bit of information I needed to narrow it down, it all makes sense now. Really puts my mind at easy as any Focus ST driver knows how fun these cars are, so I obviously want to get it back on the road. I really appreciate the help.

Being a relatively new car enthusiast, do you know where I can find that fuse? Is it car specific, or would any similar 50A fuse work fine?
 

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Thank you so much for confirming this! It was the last bit of information I needed to narrow it down, it all makes sense now. Really puts my mind at easy as any Focus ST driver knows how fun these cars are, so I obviously want to get it back on the road. I really appreciate the help.

Being a relatively new car enthusiast, do you know where I can find that fuse? Is it car specific, or would any similar 50A fuse work fine?
So I got one from a local parts store. I bought a 60A fuse.
I then went to my local Ford dealership and ordered the proper 50A fuse. It was cheap.
 
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So one thing leads to another i guess. I replaced the fuse, and now all the lights are working horn is working, and the car should start, since the og issue is fixed thanks to you guys. But, now it's saying service engine now, and won't start. Could this be caused by the constant disconnecting and reconnecting of the BCM control wire causing the BCM to be at fault? Or is this as simple as the airbox needs to be put back in and the sensors connected?

It's also saying hill descent control fault or something like that. Should I be looking at replacing all of the fuses in the battery junction box in case there are more that are cracked causing this, or am I looking at a bigger issue here?

Thanks again for the feedback.
 

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385444


I would check more than just #9.
 
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View attachment 385444

I would check more than just #9.
:\ I was able to find one at a nearby NAPA, but auto parts stores around here don't have these fuses for some reason, and neither does Ford's parts departments in the area- guess I'll have to just wait till my order online comes.

It probably is another cracked fuse. The previous owner likely gave me the deal I got for the car (2018 ST1 w 44k miles for $11,000) because he didn't know how to fix this issue. Likely what caused it is the battery that has about 3 inches of room to slide, and with constant acceleration and deceleration cause micro bends in the fuses located in the bjb in front of the battery to eventually crack them. I need to replace them all, and secure the battery.

Could it be the airflow sensor that is not attached due to the airbox being out?
 

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No that wouldn't prevent it from starting. Not having voltage to the battery junction box (front & rear) or both BCM (body control module) power supplies, #9 is one of them.

Make sure your ground points are good as well.

I strongly suggest picking up a DMM (digital multimeter) they are not expensive and will save you time and money in the long run.

J
 
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Checked the rest of them with the DMM, they were all fine and showing accurate readings. Turns out that disconnecting the battery cable, and holding the brake for 30 seconds cleared whatever code was causing that, and the car is up and running.

Thanks again for all the help!!
 

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I'm having the exact same issue! So nice to hear there are others as well and I'm not alone on this. I have a 2018 focus st base package, and here is my issue currently, and here is what I have found so far.

When I first bought the car used, I was driving it home and suddenly the throttle cuts, car sputters a little, and dies. I pull off to the side of the road with my head racing. Couple of strange things I noticed: 1. the front and rear right headlight and taillight were no longer on, 2. it was saying no key detected, but the battery in the fob was fine, and the secondary start method was not working either, telling me it's not the key, but the sensor in my car, and later findings showed it simply wasn't getting electricity.
I decide to wiggle the battery because yk, why not, I didnt want to have to pay several hundred to get it towed, and I had an interview for a job in the morning so I needed to get home and I was going to try everything I could.
I pulled on the main red battery terminal connector, and slid the battery forward, and i heard a slight beep like something finally connected. Now all the lights are on, and my key fob unlocks the doors and is being detected by my car. I hop in, and start driving, and after less then a minute, it shuts off again. I jump out of the car, pop the hood. pull the battery forward, hear the same beep, the lights are all on now and the key is now being detected. I drive the car several hours the rest of the way home.
Throughout the next couple weeks the issue continues, and I can re-create it upon hitting the acceleration which slides the battery back, killing the engine. I've checked all battery terminals, they're tight, and everything seems to work perfectly fine.
Recently, its been getting worse, and becoming more and more difficult to get started until last night, I can no longer get it to start. I decided to get precise and try to narrow down where the issue is occuring. I found after several hours of playing around with it that the plate in front of the battery where the main red battery connector goes to; if i move it less than a half inch the light comes on, but as soon as I release, they go back off and not key detected. I checked all connections and everything seems tight, and there is no corrosion. My mind is blown that I have it narrowed down to a specific small area, and still cannot find the issue, so my guess is the fuse like you are saying has a hairline crack. Did you ever get this solved?

I would absolutely love any feedback I can get from anyone, please dont tell me that it's a loose connection or a corroded battery terminal though, I've checked it all. It's something a little more precise.
Same exact issue I have had over the last couple of months, 2015 Ford Focus (SE) hatch. I have had a hell of a time finding anyone with the same issue until now.

Now I am having an issue getting any power at all until I give the positive battery cable a good tug in just the just right direction. I had the car lose all power while driving and when I finally got it started again, I did not have flashers, hill assist, or turn signals, and my windshield wipers were stuck on.

Does this all sound like the BCM 50A fuse? Battery is only 2 months old, connections are good, cables are good. This has been more frustrating than any other car/motorcycle issue I've had in the past.
 

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You really need to check the high voltage junction box in front of the battery box. A few posts above (#64) is a link to the sticky post that goes over these issues.
 

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You really need to check the high voltage junction box in front of the battery box. A few posts above (#64) is a link to the sticky post that goes over these issues.
Appreciate the reply. I am going to tear into it a bit tomorrow afternoon. I have the other page bookmarked as well for reference. I will check the fuses and the wires for corrosion, etc.

I am just perplexed on how pinching positive battery cable in the past solved it.
 

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Just replace the positive and negative cables. They are extremely cheap and it's one less item to concern yourself about.
 

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I actually have a replacement positive cable. I’ve checked both, but I will throw it on while I’m doing all this. I’ll look for a negative as well, but I had thought I had the issue pretty well narrowed down to the positive connection/plate.

I took a video before it went downhill and just pressing my thumb on the positive connection to the front plate turns the headlights on and also gets rid of the “no keyvdetected” issue. That was all I had to do to get it started when the issue was still only intermittent. Hopefully we’ll see tomorrow. I’ll post an update just Incase it’s something different that someone else may run into as well.
 

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Really look at the mega fuses. They are easily broken.
 
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