Has anyone (successfully!) replaced the BCM on their SMax (though I expect the procedure is very similar for other models)?  Can it be reprogrammed/coded with ForScan or does it need dealer software?
I believe this unit is also referred to as the GEM unit?

I think early (pre-2010?) are GEM, after, it's BCM?
Why does it need replacing (windscreen washer pump fluid leakage on PCB or ?)
Again, (need confirmation), you can program in Forscan by recording"as built" and then loading that onto replacement BCM
BUT replacement has to be same part number, exactly, however last letter can be same or higher.
Not to be taken on lightly without checking and getting definitive advice from someone other than me!

BCM in all smax

Yes ForScan can do the job

 

thats a fiesta but same process really

Thanks - good tips.  The reason I am considering it is because my interior roof lights are not working.  The only common point is the BCM.  

It's not a wiring issue because I was pressing the button when they all went off and never came back on again.  Something has definitely "gone".  The buttons in the switches are still illuminated (and the "off" button changes colour when you press it) but nothing will turn the lights on.  The headlights also do not come on when I unlock the car (but are working fine when the ignition is on).

try fuse 17 on the bcm

The fuse box in the passenger footwell?  That's listed as "F17 5 Steering wheel vibration actuator"?

22 minutes ago, Swearwolf said:

try fuse 17 on the bcm

I found the handbook list needed to be very carefully inspected and the multiple uses of the different fuses that vary by model determined.

I agree that all the simple things like fuses should be checked first (and assume there is no damage to the PCB from the washer pump cause i mentioned?)
Plus, is the difficulty and expense (if you can even get the part) worth it?
Have you tried looking at the state of the switch operation and actuating the lights in Forscan to see if you can definitely confirm where the fault lies (sorry if that has been done)?

Good call about trying to switch things with ForScan, hadn't thought of that.  I guess I can also check if the door open/closed positions are being correctly read?

Fuse F3 on my car (passenger footwell) is interior lights but that covers all the lights and the footwell and luggage compartment lights are still working fine.

have you done a fault code read on forscan? it should show an error in the BCM for the interior lights if there's one

Yes, I did a fault scan (attached)- no fault codes for the interior lights but plenty of others!  I cleared them and the only one that persists is the rear camera, which is another frikking electrical thing on the tailgate that I need to fix.

I think it's still worth me checking out the live values to see if it correctly registers the door positions and what it thinks the light status is.  If it's not the BCM there is nothing else in the circuit I can see that would cause all 4 roof lights to simultaneously stop working?

2026-01-10 DTCs.txt

Which of these type of interior light switch do you have ?

https://www.fordservicecontent.com/Ford_Content/catalog/owner_guides/ENUSA_CG3533_GLX_og_201204.pdf

See page 61 and 62

The one in the bottom left of the second page - "Side mounted lamps" - 3 buttons

Have you tried the light reset ?

• All doors closed.
• Ignition On.
• Press button 'B' for 2 seconds.
• Switch Off Ignition.
• Open drivers door, and all lights should come on.

I didn't know about that little trick!  Will try that now.  Do I need to be holding Button B when I switch the ignition off?

Alas, no.  It didn't work:( Thanks for the suggestion though

I'd suspect the light fitting before I'd go down the road of the BCM.

Those type of lights are more than just a couple of switches and a lamp. They are actually electronically controlled by their own mini processor and I've seen post in the past about the units going faulty.

I've never taken one apart myself but would guess that the switches are momentary buttons that press on a silicon pad with a carbon coating. Perhaps worth looking at getting a replacement from eBay or similar. Make sure you get the exact same part number if you do decide to replace it.

Cheers - I've replied and moved my reply back to my thread on the Interior Lights here: