At the rear of the fuse box where you pulled the fuse, there is a taillight relay. It could be sticking and causing the taillights to stay on intermittently.
Try swapping the taillight relay to see if it resolves the problem.
To test if it is the light switch, unplug the light switch connector under the steering column and light would go off if it is the cause.
Wednesday, March 27th, 2019 AT 5:46 PM