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Discussion Starter · #1 · (Edited)
*Updated to add mention of the AGS causing a communications problem with the alternator and battery light. 11/28/2020

05/27/2021 - BMS manual reset procedure added courtesy of @ddfred

07/12/2021 Ford part number for fuse added

07/18/2021 Added full location, description, and Ford part numbers for all Midi bolt on fuses. Also attached is a cross reference for aftermarket fuses for online or non-dealership purchases.


So recently there has been more and more members having odd electrical issues with their ST. Some out of the blue, some after changing their vehicles battery or others after performing modifications.

Well if your vehicle isn't detecting you key fob even though it's had the coin cell battery replaced or if you can't seem to get the vehicle to start / randomly dies but restarts will no DTC (diagnostic trouble code) start here.

Your vehicle has several components that require power to operate. All these components need to boot up and begin communicating with one another before you can even start you vehicle, yet you also need enough available voltage to engage the starter. You're asking this magic box of power to do alot.

A standard 12 VDC battery is considered discharged (completely dead) anywhere below 12 volts.

  • 12.65 - 12.77 = fully charged
  • 12.45 - 12.54 = 75% charge
  • 12.24 - 12.29 = 50% charge
  • 11.99 - 12.06 = 25% charge
  • 11.75 - 11.89 = Dead ☠
So keep that in mind when considering the age and condition of your battery. Every batteries that test "good" can have damaged cells from repeated discharges below 11 volts. Jump starting a battery that is below 11 volts can be extremely destructive to the battery, the alternator and in the worst-case scenario you should it decide to explode. (I have witnessed this first hand. Never jump the dead battery when hooked to the negative ground terminal. Always hook to the engine or chassis ground on the dead vehicle and allow the vehicle to sit and charge for awhile before attempting to start, please!)

Battery is good or brand new, time to move on.

So next you need to check that the battery terminals are clean, dry, and tight. The geniuses at Ford decided to almost fully enclose the battery for esthetics. Well charging lead acid batteries produce hydrogen gas. Hydrogen is corrosive so it makes perfect sense that they want to keep it contained to a small space to destroy the terminals and cables. (Assholes!)

Corrosion on either the negative terminal / cable / BMS (battery monitoring system) sensor can cause all sorts of strange things to happen. Even a small amount of corrosion can add additional resistance to the vehicles electrical system throwing everything off.
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Ford # (AV6Z-10C679-P)

Checking that the other ground points have been addressed as well is also advisable (Here).

Corrosion on the positive cable / terminal / BSM feed wire (white wire) can be a a problem. Even if the terminal looks clean and tight corrosion could leach down the smaller wire than is attached to the terminal trapped in corrosive gas. I suggest cutting the wire wire back and attaching it to a ring terminal inside the HVJB (high voltage junction box) to prevent damage and this also allows you to use your own positive cable and not be stuck with the Ford specific part number. (CV6Z-14300-A)

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And finally the main event.

As mentioned above the HVJB (high voltage junction box) is the main power distribution point for the entire vehicle. Most people aren't even aware of it's existence until they have an issue with it.

The junction box is connected to the battery at the end of the positive battery cable at the top of a distribution plate. The plate feeds the various systems through either MIDI or Mega fuses.

The HVJB is attached / integrated into the battery box itself.
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These fuses are very susceptible to damage. Caution needs to be taken when changing the battery that the box isn't struck or that the cables aren't over stressed in a way that might break the fuses.

I have seen these fuses test good with a DMM (digital multimeter) only to be hiding a very small break in its filament. Shock / vibration / thermal cycling all can play a part in the premature failure of these fuses. These fuses can be purchased at the parts store but the Ford part number for the 50 amp is CV6Z-14526-CA

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If the vehicle fails to detect the key fob or if it refuses to start (especially after a battery change) the integrity of these fuses. Be warned that you may or may not be able to see the damage. Remove the fuse and flex is slightly to see if the filament inside loses continuity.

Test can be performed by placing the red and black leads of a DMM on either end of the fuse and setting the meter to either continuity or ohms and checking the display output.

To learn more about how to use a DMM:

Or to learn more about electrical troubleshooting:


Anyway hope that this helped and possibly even solved you issue.
Thanks for taking time to read through this post and as always if you need help or have questions please don't hesitate to ask.

Stay Safe
J


* Updates below:

11/28/2020 - Recently there has been a rash of complaints regarding the AGS (active grill shutters) triggering a battery charge light to illuminate.

Related post (1) & (2).

The issue could be caused by water intrusion into AGS connector or from a failure of the AGS motor itself. The majority of ST owners remove the AGS entirely so this issue seems to be isolated to those members that still have theirs installed.

Here are two videos that may help determine if the AGS is the issue or if the alternator is failing. As always do not discount chafed or damaged wiring and check accordingly.

&
&


05/27/2021 - BMS manual reset procedure courtesy of @ddfred

To reset the BMS manually...Steps 2-4 have to be done in 10 seconds...
1) turn on lights
2) ignition on but do not start engine
3) flash bright lights 5 times
4) step on brake pedal 3 times...wait...
5) engine light will flash 3 times
6) battery light will flash twice...your done


---
07/18/2021

So to help clear up the confusion caused by Ford and their BS terminology I wanted to post this regarding the fuses located inside the HVJB (high voltage junction box) more and more members are seeing issues here. Attached below are a description, location & both the Ford & aftermarket equivalent for each fuse.
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Even though Ford labels these as "Mega" that are not a Mega fuse. Mega fuses have much larger physical dimensions.

These are "Midi bolt on" fuses. And they can be easily broken. Without a DMM (digital multimeter) or a test light diagnosing these can be a real PITA.

394065


Very little supports the internally. Do don't rely on a wiggle test as you are more likely to damage them. If you damage one it can leave you hunting all manner of crazy issue as you probably know if you've read this far.

The factory part numbers are as follows:

1. PSCM (power steering control module) - 80 amp, Ford # 2S6Z-14526-FA

2. Main Fuse Starter / Alternator - 150 amp, Ford # CV6Z-1526-A

3. BJB (battery junction box) - 100 amp, Ford # CV6Z-1526-GA

4. BCM (body control module) - 50 amp, Ford # CV6Z-1526-CA

5. Not Used

6. RJB (rear junction box) - 70 amp, Ford # CV6Z-1526-EA

7. Not Used

8. BJB (battery junction box) / Engine cooling fan relay - 50 amp, Ford # CV6Z-1526-CA

9. BCM (body control module) - 50 amp, Ford # CV6Z-1526-CA

10. Not Used

The aftermarket replacements can be located just about anywhere. Here is the Littlefuse guide by amperage.

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Remember that these are called Midi bolt on and not just Midi fuses.

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*Last note: Do not use aftermarket fuses to rreplace #2 Main Fuse. Only use Ford replacement.

It is also worth noting that the nylon lock nuts that hold these fuses are considered a single use item. To prevent them becoming loose you should either replace them with either a new stainless nyloc nut or nut and split ring lock washer.

The size is 5M x 0.8


J
 

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Discussion Starter · #2 ·
A few other if your also interested.

 

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Hi, so I had this happen to me and trust me it's not pretty. The battery I had in my car started pulling acid through the terminals. It was so bad that the BMS plug and cable was completely destroyed. I will attach pics to show the damage. Apart from that the the whole area around the battery box, all attaching hardware and cable clips all melted from the acid.

The amount of corrosion that followed was a nightmare too and I had to treat all the contaminated areas and get some new hardware and the brackets for the clutch cables and selector cables plated. The gearbox mount I had to replace and the bracket above it plated as well.

All in all I came to find out the battery I was suppied was a battery rated for a Focus 1.6. Not the Focus ST EcoBoost. The cold start rating was too low and the ampere hour rating was also not correct so the electronics in the car was drawing too much load. Thus my issue.

The unfortunate thing is that most of this is hidden when the battery top cover is on so without doing a visual inspection every so often you will never see the terminals unless it's too late or you having an electrical issue.


Images when it happened

Auto part Fuel line Engine
Reptile Lizard Scaled reptile



After all my hard work

Yellow Auto part Vehicle Engine
Auto part Engine Motor vehicle Vehicle Fuel line
Engine Auto part Vehicle Car Automotive engine part
Engine Auto part Vehicle Automotive engine part Fuel line
 

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All in all I came to find out the battery I was suppied was a battery rated for a Focus 1.6. Not the Focus ST EcoBoost. The cold start rating was too low and the ampere hour rating was also not correct so the electronics in the car was drawing too much load. Thus my issue.
Did you ever find out who supplied that battery? Previous owner being dumb, auto store rep not paying attention? Factory? Dealer? Im just so curious to hear who/if you tried to hold someone accountable for that nightmare? Thanks for sharing good reminder to check your battery often everyone. I try to make point of opening my hood and check the oil every time I gas up, but I dont always check the battery, until now that is.

Hey while we are on the battery subject. I went ahead and took some of the forum advice to put in a larger battery as per link below. Worked really well. I just would hate to have an issue like this guy Im quoting, having additional ampere & crank should only be a good thing right? I am running a 1000 watt amp so I figure this upgrade is almost necessary.

 

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Thanks for this...My car has been acting sorta strange lately with key fob not being noticed while sitting in the car. First time I just locked the car with key fob and unlocked, seemed to work. I didn't think it could be the battery or electrical issue...that's disheartening. Hopefully just a key fob battery...have to replace soon.
 

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@DanSTmk3 i bought my ST with an improper sized battery already installed as well, but after reading all the gremlins these cars have with battery issues, i quickly bought the correct BCI battery. Your post just solidifies my decision.
 

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Did you ever find out who supplied that battery? Previous owner being dumb, auto store rep not paying attention? Factory? Dealer? Im just so curious to hear who/if you tried to hold someone accountable for that nightmare? Thanks for sharing good reminder to check your battery often everyone. I try to make point of opening my hood and check the oil every time I gas up, but I dont always check the battery, until now that is.

Hey while we are on the battery subject. I went ahead and took some of the forum advice to put in a larger battery as per link below. Worked really well. I just would hate to have an issue like this guy Im quoting, having additional ampere & crank should only be a good thing right? I am running a 1000 watt amp so I figure this upgrade is almost necessary.

Did you ever find out who supplied that battery? Previous owner being dumb, auto store rep not paying attention? Factory? Dealer? Im just so curious to hear who/if you tried to hold someone accountable for that nightmare? Thanks for sharing good reminder to check your battery often everyone. I try to make point of opening my hood and check the oil every time I gas up, but I dont always check the battery, until now that is.

Hey while we are on the battery subject. I went ahead and took some of the forum advice to put in a larger battery as per link below. Worked really well. I just would hate to have an issue like this guy Im quoting, having additional ampere & crank should only be a good thing right? I am running a 1000 watt amp so I figure this upgrade is almost necessary.

So basically the battery centre where I took my car after the OEM battery started giving me issues due to age and not holding capacity, they replaced the battery for me. And the invoice and the battery spec sheet that they have that goes by car manufacturers and the models in each category they "supposedly" replaced it with the same specs as OEM..

Stupidly I should have realzise it was not the same because the battery didn't even last 2 years. And at the time my car was bone stock. So when this happened and I went back to them with the battery and showed them the pictures, they basically said that firstly the battery only has a 1 year guarantee, and second they cannot be held liable for damage because in a 2 year period I could have "missused" the battery or I have a aftermarket sound system in the car or I could have left my lights on... so the list goes on.

But yeah it was no point because unfortunately I didn't go to a ford dealer to get a battery but I guess its things like this that we live and we learn. So now i check every aspect of my car on a weekly basis.
 

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@DanSTmk3 i bought my ST with an improper sized battery already installed as well, but after reading all the gremlins these cars have with battery issues, i quickly bought the correct BCI battery. Your post just solidifies my decision.
I'm glad you made that change and hopefully these posts and discussions help all our Fellow ST members
 

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Discussion Starter · #10 ·
Updated main post to include AGS & Battery light on.

J
 

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Hi, so I had this happen to me and trust me it's not pretty. The battery I had in my car started pulling acid through the terminals. It was so bad that the BMS plug and cable was completely destroyed. I will attach pics to show the damage. Apart from that the the whole area around the battery box, all attaching hardware and cable clips all melted from the acid.

The amount of corrosion that followed was a nightmare too and I had to treat all the contaminated areas and get some new hardware and the brackets for the clutch cables and selector cables plated. The gearbox mount I had to replace and the bracket above it plated as well.

All in all I came to find out the battery I was suppied was a battery rated for a Focus 1.6. Not the Focus ST EcoBoost. The cold start rating was too low and the ampere hour rating was also not correct so the electronics in the car was drawing too much load. Thus my issue.

The unfortunate thing is that most of this is hidden when the battery top cover is on so without doing a visual inspection every so often you will never see the terminals unless it's too late or you having an electrical issue.


Images when it happened

View attachment 385057 View attachment 385058 View attachment 385059


After all my hard work

View attachment 385060 View attachment 385063 View attachment 385062 View attachment 385061
Howzit bud, so what is the correct battery to have
 

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hi all i went to my car this morning and had nothing from my key to unlock the car so i used the key in door and then key in slot to make my car run but i was getting no dash at all now all function in the car has stopped working any help please as been looking at this for a week trying different things even new battery and bcm but still nothing need help please as driving me mad
 

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Discussion Starter · #14 ·
Have you tried the things mentioned in this post?
 

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hi pal i have tried as much as i can when i wiggle the middle blue connector on the bcm i get it to come on but soon as i let go it all goes off again i have tested all connectors and are ok
its driving me crazy and as my mrs works for the nhs on front line and she uses my car to go to work in i need it back up and running asap
 

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Discussion Starter · #17 ·
Well it sounds like you either have a dirty or damaged female pin inside the connector or an issue with the male pin inside the BCM.

It could be corrosion or possibly a cold solder joint that has cracked it the issue is resolved with pressure but continues after that pressure is released.

How comfortable are you with electronics? What kind of tools do you have?
 

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Well it sounds like you either have a dirty or damaged female pin inside the connector or an issue with the male pin inside the BCM.

It could be corrosion or possibly a cold solder joint that has cracked it the issue is resolved with pressure but continues after that pressure is released.

How comfortable are you with electronics? What kind of tools do you have?
mechanic for over 18 years i have fixed the earlier ones were the solder has gone on the mk2 fords, i have replaced the bcm and same thing, and doing exactly the same, that's why i am end of my wits with it, only had this a year, i am fully tooled with everything,
 

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Discussion Starter · #19 ·
386784
386785
386786


Which connector are you pushing on?
 
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c2280f if i pull it out and just wiggle it it comes on i have even took the covers off the bcm to see if they have got dry joints on them but as far as i can see and tried moving the connectors all seem fine,
 
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