Having a strange problem with my 04 1500 2WD. Both main brake lights are not coming on when brake pedal depressed. Third brake light DOES work, as do turn signals and flashers. LAMP OUT indicator is on. In addition, my trailer harness is energized even if the key is off, and my battery seems to be draining slowly if the truck sits for some time.

I don’t think it’s the MFS since the indicators all work. I fear it’s the TIPM - if so, it’s probably the end for this truxk.

Any suggestions as to where to start looking? Hoping this will be an easy fix, as a major electrical problem would not be worth fixing given the age and mileage on the truck. I drive it only very occasionally, usually as a haul or tow vehicle only.

Thanks.

 

I recommend removing the brake lights and see what's in there. It could be burned out bulbs, wrong bulbs, poorly wired LED conversion, or rust.
For your trailer plug, which pins are staying energized? If it's the tail lights then you may have a faulty brake light switch.
Consider getting one of those probe testers for troubleshooting electrical problems. They really make the process easier, and the analog testers are around $30.

 

Bulbs seem okay as flashers and turn signals both work. Brake switch seems okay since third brake light works. Trailer running light and one brake light seems to be energized even with key off. Going to dig in more this morning after it warms upna bit.