Brake lights don't work when engine runs

[Kabrondaz]

I'm having an issue. Brake lights work with the engine off or ignition off, when I step on the brake pedal, but as soon as I start the engine or turn on the ignition, brake lights go off and no longer work when I step on the brake pedal, I'm talking about a 2017 explorer sport 3.5 with led taillights, it only affects the brake lights, everything else works, turn signals, reverse, and tail lights work, I already replaced the brake switch. And checked all fuses.

 

[peterk9]

I'm having a similar issue, brake lights work with the engine off or ignition off, when I step on the brake pedal, but as soon as I start the engine or turn on the ignition, brake lights go off and no longer work when I step on the brake pedal, I'm talking about a 2017 explorer sport 3.5 with led taillights, it only affects the brake lights, everything else works, turn signals, reverse, and tail lights work, I already replaced the brake switch. And checked all fuses.

Welcome to the Forum.
What happens when you just put it in accessory mode? Do they work then?

Peter

 

[Kabrondaz]

They work when everything is off, once I activate accessory mode, or turn on engine, they turn off and won't work at all until everything is off again.

 

[tfach]

Is it possible that the stop light switch isn’t in all the way or adjusted properly? If everything else is working properly except your brake lights when the vehicle is on I would start from there again. Remove it, adjust it, and reinstall.

 

[peterk9]

They work when everything is off, once I activate accessory mode, or turn on engine, they turn off and won't work at all until everything is off again.

I wonder if it could be a problem with a control module like the Lighting Control Module (LCM) or Body Control Module (BCM) since the lights work without the electrical system being powered? Just a guess and I'm not sure how to check for that.

Peter

 

[Kabrondaz]

I replaced the brake switch with a new one, and before I installed it I tested it by pressing it in and out, and it was the same issue, I'm thinking it might be the wiring, does anyone have a wiring diagram for the tail lights by any chance?

 

[peterk9]

I replaced the brake switch with a new one, and before I installed it I tested it by pressing it in and out, and it was the same issue, I'm thinking it might be the wiring, does anyone have a wiring diagram for the tail lights by any chance?

Just FYI, those control modules have nothing to do with the switch. Check the links in this post to see if they might help. 2014 seat wiring diagram or connector view

Peter

 

[ProjectSHO89]

I'm having a similar issue, brake lights work with the engine off or ignition off, when I step on the brake pedal, but as soon as I start the engine or turn on the ignition, brake lights go off and no longer work when I step on the brake pedal, I'm talking about a 2017 explorer sport 3.5 with led taillights, it only affects the brake lights, everything else works, turn signals, reverse, and tail lights work, I already replaced the brake switch. And checked all fuses.

Well, actually, your issue is nothing like the OP's... This issue would best be split off into a new thread for clarity.

Is the high-mount stop lamp behaving the same as the corner stop lamps or does it work correctly when the brake is applied and the ignition is not in the OFF position?

Do the rear (and other) turn signals behave properly when the ignition is ON and both when the brake pedal is applied and then released?

Neither fuses nor switches would cause this issue, it's probably a logic or internal BCM issue. You'll need a capable scan tool or comparable to see what's actually going on in there.

 

[peterk9]

............................ This issue would best be split off into a new thread for clarity........................................

Done. Moved to its own thread with slight edit to original post. Thank you for bring this up.

Peter