2019 Gen2 Brake Lights stopped working

[julien194b]

yes , the green circle of your picture show the OEM rear light when put transmission in R, it's usual, they use this place for turn signal in Europe and add another rear light...After opening the rear it's important to make waterproof again which has not been done properly on yours and may explain your problem. I think and hope you should manage to fix that easily.

 

[FordTechOne]

Thanks for the link. That's just what I was searching for.

Update on the problem: it seems there was modification done as @julien194b suggested. Also there was a significant amount of water in both lights...
I will work my way through the wiring diagrams and check where the last connection is with a working brake light and turning signal. Mass contact seems to be ok since the red rear DRL is working just fine.

In the picture below, when does the highlighted section of the rear light normally turn on?

View attachment 441424

That’s the reverse lamp.

 

[smurfslayer]

yes , the green circle of your picture show the OEM rear light when put transmission in R, it's usual, they use this place for turn signal in Europe and add another rear light...After opening the rear it's important to make waterproof again which has not been done properly on yours and may explain your problem. I think and hope you should manage to fix that easily.

I am hoping that since @Jonas_W is not reporting “many DTC from different modules” that water intrusion may have been caught soon enough and maybe it is just wiring right now. However, the BLIS module(s) are probably toast.

 

[Jonas_W]

Thanks for all the replies. So it seems they added the indicator to that section of the rear light. There is an extra cable fed into the light and being soldered on there. It's all just from visual inspection and unfortunately I'm home sick, so I can't work on the truck right now.

You can also here an indicator relais in the rear clicking when turning on the indicator (might be fro the EU trailer socket). So I guess the signal from the BCM is clearly back there. Water might just have broken some functions of the rear lights...

When driving the truck to my shop the day before yesterday it was throwing errors for automatic park brake and hill start assist if I remember correctly.

 

[rschap1]

Good luck with diagnosis and repair

 

[FordTechOne]

Thanks for all the replies. So it seems they added the indicator to that section of the rear light. There is an extra cable fed into the light and being soldered on there. It's all just from visual inspection and unfortunately I'm home sick, so I can't work on the truck right now.

You can also here an indicator relais in the rear clicking when turning on the indicator (might be fro the EU trailer socket). So I guess the signal from the BCM is clearly back there. Water might just have broken some functions of the rear lights...

When driving the truck to my shop the day before yesterday it was throwing errors for automatic park brake and hill start assist if I remember correctly.

Those symptoms aligns with the water in the tail lamps. The medium speed CAN bus runs to both SOD modules in the tail lamps. If those circuits get shorted together, to ground, or to power, it pulls down the entire network. Then you get various error messages for systems on MS-CAN.

 

[CleverGirl_]

Thanks for all the replies. So it seems they added the indicator to that section of the rear light. There is an extra cable fed into the light and being soldered on there. It's all just from visual inspection and unfortunately I'm home sick, so I can't work on the truck right now.

You can also here an indicator relais in the rear clicking when turning on the indicator (might be fro the EU trailer socket). So I guess the signal from the BCM is clearly back there. Water might just have broken some functions of the rear lights...

When driving the truck to my shop the day before yesterday it was throwing errors for automatic park brake and hill start assist if I remember correctly.

Sounds like they may have added in a flasher system. I'd check the headlights too.

 

[Jonas_W]

Quick update:
I checked for DTCs with ForScan and there isn't really an issue with the BCM logged. It only stored errors when I took off the brake switch and when I was running the car without the rear lights plugged in. Furthermore I can display/log the voltage output when braking or indicating. So everything seems normal from the BCM's side.

I was digging deeper into the wiring underneath the car though. There was quite some modification to the wiring done to the car. On the photo below you can see they installed three relais. My guess is, they use two for the indicators and one for the brake lights. I will replace all relais and see if that helps.

 

[smurfslayer]

Those relays don’t much look weather resistant. They don’t even look like they pretend to be weather resistant. I’d start there.

I added baja designs squadron lights to the rears and wired to reverse circuit off the trailer hitch connection and to up fitter number 6 by using a relay. This relay was advertised as weather resistant. It wasn’t. On night I was in the kitchen and could see my neighbor’s back yard. All of it. I just thought he upgraded his motion sensor lights, came out the next morning and went on my way. 2 nights later, I see the same thing, neighbor’s back yard completely lit up. It’s not like him to leave things on all night so I went out and checked, found my squadrons on... Truck was off, but the squadrons were on. I was able to cycle the relay by turning up fitter 6 on and off. When I took the wiring apart I found the relay completely soaked - water got in, but didn’t get out. Brilliant. fixed it by wrapping in rubber and then electrical tape, despite the “weather proof” assembly.