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Discussion Starter #1 (Edited)
We got a lot of snow this year and I got to drive a lot in limited visibility conditions. I decided I wanted to install the rear fog the European RS' have. I'll gather all the information I can in this thread (will update as I move along the steps) and use it to search for help with the wiring (hoping to figure out if it can be wired to the BCM and use the euro headlight switch with rear fog button).

Here we go! As I said I'll update this every step of the way. Posting this in the lighting section as I'm doing it for the purpose of adding the light, not for aesthetics of having the euro diffuser!

Step 1) Parts

Diffuser: P/N G1EY-17F954-A
--> Bought mine on eBay UK (used), also available from Ford Parts UK if you send them a part inquiry. I read on some other posts it was about 120GBP.
Rear Fog Light: P/N G1EY-15K272-A (also found it listed under P/N 2009072)
--> Found some listed on eBay UK, Ford Parts UK has it listed on their site for 185GBP which is really pricey!
--> Found some alternative, will confirm about fitment once received:
1) LuxVision (shipped next day from UK, in stock, similar design to the Ford unit): https://www.carbuildersolutions.com/uk/55mm-led-fog-light-with-clear-lens
2) Hella (6 weeks special order, looks identical to the Ford unit): https://www.rallylights.com/hella-55mm-led-turn-reverse-or-rear-fog-lamp.html
Headlight Switch: Found one used on eBay UK, simply look for one that looks as shown below (with rear fog button instead of hatch open button). Make sure it's not the one with the headlight beam adjustment button at the middle of it which is the most current one it seams.

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Step 2) Headlight Switch Installation

I've done this already, once replaced the euro switch activates the rear fog indicator in the instrument cluster...hopefully this is good hope that the BCM actually has an output for the rear fog.

1) Pull back the door seal as required for dash side panel removal:
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2) Remove the dash side panel, start from the bottom and slowly pry the 3 metal clips out as shown below:
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3) Reach the back of the headlight switch and push it out...it comes out really easily, it's only held in place by the 4 small flexible metal tabs, disconnect wiring harness at back of switch (note the switch P/N seen below is the NA switch P/N, sorry I did not note the euro switch P/N, see step 1) for buying tips based on switch appearance):
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4) See below the euro and NA headlight switch, install in reverse order (I know my dash trim around the switch is broken, found it broken after someone posted about this issue, will not bother about it):
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5) Notice how the rear fog button now activates the rear fog indicator in the instrument cluster when pressed (requires the headlights to be on, might work with the corner lights only too I think):

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Step 3) Diffuser Replacement and Fog Light Mount

Our NA rear bumpers do not have the mouting provision for the rear fog light (see pictures below of the UK bumper cover light mount). I will post information on how I mounted the light once completed. I did get a picture from another member who mounted the rear fog light using small brackets (see below). I'll either use this idea or fiberglass a mounting flange or depending on fitment mount it to the diffuser itself. Diffuser replacement should be pretty straight forward though (same mounting tabs/points).

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Step 4) Wiring

To be updated once I figure it out (will need help)!

I hope there is a way to make use of the euro headlight switch to control the rear fog through the BCM. I found it has been done on Fusions so hopefully it can be done on our cars.

Otherwise I will wire it to a switch located somewhere within reach and view of the driver seat...plan B!

Step 5) Forscan

Might be required to activate the rear fog output from the BCM...
 

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Discussion Starter #2
Basically what I need now is some help with the BCM / RS wiring.

Anybody here known for their knowledge of the RS wiring and BCM?

I'm hoping we can simply add a pin in en empty connector slot at the BCM and get the trigger for the rear fog working. Although it might not be as simple as this. I can execute the work no problem but need help figuring out where to pickup the signal from...if that is even possible.

Please let me know if you think of a member I should write to for some help to get started!

I wonder how different the BCM outputs are between the NA and Euro RS versions if anyone has the diagrams available maybe that could be a good starting point.

Thanks!
 

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Darn, I was really hoping that euro switch had a connector that I could wire into to use the rear fog button to control some aux lighting. Thanks for the DIY and looking forward to what you find wiring-wise!
 

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How would you actuate you trunk at this point? other than from the keyfob or the trunk handle?

Just curious. That's a lot of good info man! :encouragement:
 

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As far as wiring I know from base model focus reading that the rear fog light wires direct to the BCM but there was really any proof to that. Supposedly there is connector in the trunk or rear tail light area. However for easy of the wiring, could you not tap in to the parking lights?
 

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Looking at page 86-2 of the wiring diagram. Pin 10 of C2280B at the BCM goes to the rear fog light. I think the center rear goes through C431 Pin 9 to C699Pin1 fog light then back through C699 at pin 2 can through C431 at Pin 10 then to Ground G401. Wire between fog light and BCM should be RD-BK (CLS45) and from fog light to ground BK-WH (GD150).

Looking at page 151-17 C431 should be inside the rear bumper or behind the tire on the right side.

I hope this makes sense:
[BCM]>C2280B-10>----CLS45(RD-BK)---->C431-9>----CLS45(RD-BK)----<C699-1<[FOG LAMP, CENTER REAR]>C699-2>----GD150(BK-WH)----<C431-10<----GD150(BK-WH)----(S402)----G401
 

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As far as wiring I know from base model focus reading that the rear fog light wires direct to the BCM but there was really any proof to that. Supposedly there is connector in the trunk or rear tail light area. However for easy of the wiring, could you not tap in to the parking lights?
No, that is not a good idea. Not sure about the US, but I've heard in Euro if you run the rear fog lights during clear weather you can be fined. Even if there is not fine/ticket it is very rude to have that bright light on if not needed. Really should be wired with its own control (the headlight switch he already bought). Based on the fact that the LIN from the headlight switch goes to the BCM and the gauge cluster shows the rear fog indicator I'd guess the BCM is supporting it right now.
 

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Discussion Starter #9
How would you actuate you trunk at this point? other than from the keyfob or the trunk handle?

Just curious. That's a lot of good info man!
I only ever open it at the trunk. Never used the button on the headlight switch! Might bother those who actually use it though! Especially those who installed the stronger struts so their trunk actually opens when released!
 

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Discussion Starter #10
Looking at page 86-2 of the wiring diagram. Pin 10 of C2280B at the BCM goes to the rear fog light. I think the center rear goes through C431 Pin 9 to C699Pin1 fog light then back through C699 at pin 2 can through C431 at Pin 10 then to Ground G401. Wire between fog light and BCM should be RD-BK (CLS45) and from fog light to ground BK-WH (GD150).

Looking at page 151-17 C431 should be inside the rear bumper or behind the tire on the right side.

I hope this makes sense:
[BCM]>C2280B-10>----CLS45(RD-BK)---->C431-9>----CLS45(RD-BK)----<C699-1<[FOG LAMP, CENTER REAR]>C699-2>----GD150(BK-WH)----<C431-10<----GD150(BK-WH)----(S402)----G401
That it some very good info here! I actually was hoping you would post some info from other posts I saw where you had a lot of info on wiring!

Got a layout of the bcm connectors handy? I will start from the bcm and check if there actually is a wire in our NA connectors and trace if to the back of the car to see if it has voltage when the rear fog is activated.

That’s great information to get started that’s why I love this forum!
 

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Discussion Starter #11 (Edited)
As far as wiring I know from base model focus reading that the rear fog light wires direct to the BCM but there was really any proof to that. Supposedly there is connector in the trunk or rear tail light area. However for easy of the wiring, could you not tap in to the parking lights?
No, that is not a good idea. Not sure about the US, but I've heard in Euro if you run the rear fog lights during clear weather you can be fined. Even if there is not fine/ticket it is very rude to have that bright light on if not needed. Really should be wired with its own control (the headlight switch he already bought). Based on the fact that the LIN from the headlight switch goes to the BCM and the gauge cluster shows the rear fog indicator I'd guess the BCM is supporting it right now.
I dont recommend anyone to run this as a fourth brake light although you technically could!

I’m trying to make function as intended through the BCM and as mentionned use it only in bad weather (fog, snow, occasional taikgaters maybe...).

But yeah if someone wanted a fourth brake light they could easily wire it to the tails and skip the BCM part (if that turns out possible).

Personnally my plan B is to run a dedicated switch up front all the way to the fog light and use a swith with an indicator so I dont turn it on by mistake and never notice...

Edit: I see people with their rear fog on in clear weather all the time! Most of them probably dont even have a clue what this other fog light button is and just hit it all the time! Here people drive with their front fogs all the time (I do too must admit)...so it’s probably naturak for them to hit both buttons even when they dont know what the second one does! On certain cars it is indeed annoying and most likely illegal anywhere!
 

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I dont recommend anyone to run this as a fourth brake light although you technically could!

I’m trying to make function as intended through the BCM and as mentionned use it only in bad weather (fog, snow, occasional taikgaters maybe...).

But yeah if someone wanted a fourth brake light they could easily wire it to the tails and skip the BCM part (if that turns out possible).

Personnally my plan B is to run a dedicated switch up front all the way to the fog light and use a swith with an indicator so I dont turn it on by mistake and never notice...
I was saying run it with the parking lights not the brake lights. Already having the switch I would get it to run with the BCM. With out the dedicated Euro OEM switch, you could have ran wires to the current fog light switch and tapped the wires but that is a long distance for wires to run. Lets us know what you find out with the BCM
 

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I only ever open it at the trunk. Never used the button on the headlight switch! Might bother those who actually use it though! Especially those who installed the stronger struts so their trunk actually opens when released!
I have the auto trunk. I can use the key fine......

I actually prefer not having the trunk button to where it is since when you press while driving.... in my case, it will open wide on the road.
 

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OP, you are definitely motivated to make this happen! I crawled around under the car looking for the rear fog connector but it wasn't there. If we have the wiring, it would likely go all the way to the rear fuse panel in the trunk. Maybe we are lucky enough to have the wiring go that far? I'm hoping that its coiled up neatly tucked behind the fuse box. I was going to poke around back there some more this weekend when I install my dsc controller.

Thanks for confirming that the euro switch activates the rear fogs, I'm guessing that there is some logic in to tell the bcm that it's not the trunk button.

The wiring diagram are like 15 bucks on eBay if you get stuck, or pm me and I can email you all the relevant pages.
 

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Discussion Starter #15
OP, you are definitely motivated to make this happen! I crawled around under the car looking for the rear fog connector but it wasn't there. If we have the wiring, it would likely go all the way to the rear fuse panel in the trunk. Maybe we are lucky enough to have the wiring go that far? I'm hoping that its coiled up neatly tucked behind the fuse box. I was going to poke around back there some more this weekend when I install my dsc controller.

Thanks for confirming that the euro switch activates the rear fogs, I'm guessing that there is some logic in to tell the bcm that it's not the trunk button.

The wiring diagram are like 15 bucks on eBay if you get stuck, or pm me and I can email you all the relevant pages.
Thanks for looking for the connector! I doubt there is anything behind our bumpers as you said! And the euro rs also have the backup sensors back there so I guess there’s a whole harness for their rear bumper that we dont have. If there is anything near the rear fuse box I’d be happy with that, in fact I’d be happy if there only is a pin at the BCM that provides current when I hit the switch! Running wires to the back is not a big deal to me!

I hope to have some time this weekend to look at the wiring based on the infos provided by @ControlNode.

I’m definitely planning to make it happen! Worst case if the BCM way is not possible I’ll run a dedicated switch.
 

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Discussion Starter #16
I was saying run it with the parking lights not the brake lights. Already having the switch I would get it to run with the BCM. With out the dedicated Euro OEM switch, you could have ran wires to the current fog light switch and tapped the wires but that is a long distance for wires to run. Lets us know what you find out with the BCM
Sorry I read that wrong! Yeah maybe the parking lights could work too.

I was thinking I could find a switched power source out of the rear fuse box to power the light and run a switch to the front. Use add-a-fuse if required, same as wiring for a dimming mirror or dash cam out of the front fuse box.
 

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That it some very good info here! I actually was hoping you would post some info from other posts I saw where you had a lot of info on wiring!

Got a layout of the bcm connectors handy? I will start from the bcm and check if there actually is a wire in our NA connectors and trace if to the back of the car to see if it has voltage when the rear fog is activated.

That’s great information to get started that’s why I love this forum!
I'll have to look at that some other evening got an early day tomorrow and need to sleep.
 

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Discussion Starter #18
I'll have to look at that some other evening got an early day tomorrow and need to sleep.
Thanks again!

I found a generic picture of the focus bcm (2012 focus it seems) but the connectors labeling I guess should be the same. So the connector C2280B would be the top left one, I’ll have a look at it this week-end if I find the time to pull the car in the garage and work on it a bit.

Might also buy the wiring manual on ebay for future reference too.
 

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Discussion Starter #20
Found another Focus forum (German I think) which had some good diagrams of the BCM and pins numbering that I'll use to get started.

Also found some good info on a fusion forum: How to: Mondeo style Rear Fog light

The fusion forum has the P/N's for the connectors that might be used to add a pin to the connector if the pin is not wired. It also mentions there are tiny numbers to help identify pin numbers so that should help too! Hopefully if our cars are not wired all that is needed is to add a pin to the harness and start from there to create our own wiring for the rear fog. In this case I'll have to determine if a relay is recommended VS wiring it straight to the BCM output. I know how relays work but I'm not an expert at knowing when they should absolutely be used...

Now I really hope to find some time to look for pin 10 at connector C2280B over the week-end!

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