General knowledge.... brake light issues can cause transmission failure (E4OD)

paul rondelli

Rank V

Don't delete

May 21, 2020
Suwanee, GA, USA
Just read about a fellow Bronco enthusiast who burned up two transmission (E4OD) due to a short in his third brake light. The computer checks for voltage at the brake lights to determine if the brakes are engaged. This is turn causes the electronic transmission to disengage the torque converter. I had no idea that a 15$ shorted wire could cause close to 6,000 in damages to multiple transmissions.

I have to give it up to the original poster. By sharing his misfortune.. it just might save another Bronco Brother's transmission.

Moral of the story if you have issues with any brake light … do not push this off... it could be killing your tranny.

Also be aware that if you change out your brake lights to LED … research about adding a capacitor to increase draw. Since LED's do not pull enough current it might also cause your electronic tranny to act crazy.

just another reason why I drive a stick.

Bronco V-8

Rank VI

Promoter I

May 29, 2020
Member #


Interesting ,wonder if that is why my 150 tranny freaks out on occasion.
and yes another reason to drive a manual.