2020 Expedition Max no power to passenger brake light

[kierobi]

Replaced brake lights/rear lights in Wife's Expedition Max XLT more than a year ago and they've worked no issues. Installed with the Load Resistor Kit so no hyper flash etc.

She got told today by a friend following her that her passenger brake light is out. I checked it when she got home and rear light is working but brake light is not, although they are same LED. Started fault finding and no power to bulb socket when lights are switched off and brake pedal is pressed. Confirmed I'm testing the right tab by checking on Driver's side. Disconnected at the pigtail and no power to the pigtail socket for the brake light. Again, checked on the Driver's Side and confirmed I was testing the right hole on the socket for the pigtail.

Tried testing the LED and LED Load Resistor Kit and was able to get it to light up, but don't know if that was just the tail light because connections I was using for testing are pretty big.

Did note that the little splash guard wasn't all the way "sealed" and some water got behind the light and onto the LED resistor heat sink but don't know if that would have been enough to short it or not.

Can anyone tell me next step for checking? I looked in the owner's manual and can't find a fuse for these lights and would think that from this pigtail it would run all the way back to the brake pedal or control system somewhere.

Thanks in advance!

 

[kierobi]

Links to the LED kit I put together for the conversion in case anyone thinks it'll make a difference. Like I said these have been working flawlessly for more than a year.

Amazon.com

Amazon.com

 

[Benztech]

I would start by bypassing or removing the resistor. Or you could compare resistance of both sides to check for any difference.

 

[kierobi]

I would start by bypassing or removing the resistor. Or you could compare resistance of both sides to check for any difference.

I kept the old bulbs and so removed the LED kits all together and put the bulbs in but no brake light. Tail lights work but brake light still not.

With the LED installed with resistor kit, tail lights work but brake lights don't so I don't think it's an issue with the resistor. Swapping it over to the Driver's side it works both tail light and brake light too.

Just started trying to check the brake light switch but as soon as you remove it from the bracket it doesn't work so makes testing it kind of hard!

 

[kierobi]

So disconnected the pigtail at the brake switch and started testing at the pigtail to see if the switch was defective. Ended up blowing the fuse and no spares to had to swap it around for now. No Synch for the wife tomorrow!
I was able to jump between 12V in and one of the wires going out and brake lights came on EXCEPT passenger side. Starting to think I might have a break in the wire somewhere...

EDIT: found the service manual on a thread here and started digging into it some more. Tried the passenger side turn signal and get the hyper flash on the instrument cluster and no turn signal. Looking into the manual, think I need to try and locate the output from the Body Control Module and check the connections there. Wouldn't have thought that there would have been three separate outputs from the BCM to the brake lights, but that's what the manual is telling me. Now just to get the new fuses in and see if I can't find a loose wire.

 

[Mr Big]

So disconnected the pigtail at the brake switch and started testing at the pigtail to see if the switch was defective. Ended up blowing the fuse and no spares to had to swap it around for now. No Synch for the wife tomorrow!
I was able to jump between 12V in and one of the wires going out and brake lights came on EXCEPT passenger side. Starting to think I might have a break in the wire somewhere...

EDIT: found the service manual on a thread here and started digging into it some more. Tried the passenger side turn signal and get the hyper flash on the instrument cluster and no turn signal. Looking into the manual, think I need to try and locate the output from the Body Control Module and check the connections there. Wouldn't have thought that there would have been three separate outputs from the BCM to the brake lights, but that's what the manual is telling me. Now just to get the new fuses in and see if I can't find a loose wire.

See if you can start from the socket and test backwards to find where you are losing power. I had a similar issue and used a pic light and found a socket connection under the vehicle that was not making contact. I disconnected it, cleaned it, dielectric greased and plugged it back in. It solved the problem. So, I went further and performed the same maintenance on all socket connections I could get to.