We had an odd situation with our 3rd gen Toyota Tacoma recently, and wanted to share our findings and resolution in case anyone else runs into this issue. It all started while we were backing up and parking the truck, the instrument cluster beeped, and a scary warning message appeared on the dash which read "Brake Override Malfunction - Visit Your Dealer". Even though we have experience working on vehicles and their electrical systems, we were very frightened by the message. Unsure of the direct cause, we parked the truck and restarted it, no warning message. Perhaps it was a fluke, we thought.

We ended up driving the truck all the way back to the office without any issues, braking plenty of times along the way. It was only when we were parking the truck, that the warning message came back. This time, the check engine light came on along with the "TRAC OFF" indicator, meaning the traction control system was inoperable. This happened right as we were backing up the truck into its parking spot. We were quite concerned at this point. While the brakes were physically working, a brake system malfunction is not exactly our idea of a good time! Also, losing traction control may be fun to some, but is quite dangerous on slick roads and during rain. We read the DTC codes with an OBD2 code scanner, which revealed one trouble code: P0724 - Brake Switch B Circuit High. Okay, so we were a bit relieved at this point because while a brake switch is a critical vehicle component, they are known to fail, and are very easy to replace. Originally, our plan at this point was to just purchase and install a new brake switch and call it a day. The dealer is right down the road and the install would probably take under 5 minutes. We of course inspected the brake switch first and noticed no physical damage, and ensured the connector was in good condition. Still, we were just planning to replace it as the failure was likely within and not visible, and it's a cheap part.

However, since we can't control our curiosity, we decided to consult the factory service manual for the 3rd gen Tacoma and look up the P0724 DTC code. Much to our surprise, we found some additional information in the DTC table. According to the factory service manual, P0724 (P070312) actually corresponds to a "Brake Switch B Circuit Short to Battery". Interesting right? While we suppose it's possible for a brake switch (or the wiring) to fail in such a way that causes a short to the positive (battery) rail, that is actually quite unlikely. The more likely scenario would be that some other component of the vehicle was causing a brake switch circuit short to battery.

We did some additional research and actually found an article on Tacoma World about someone with the same DTC code. The likely cause in their situation was a ground fault or short in the brake light system, which ties in directly with the brake switch circuit. This prompted us to investigate the truck and see if we could figure it out. We started by inspecting all the brake light connections and harnesses for damage or exposed wiring. Even corrosion or water intrusion can cause an issue like this. We did not find any obvious issues. At this point, we moved on to a typical lighting test. Having someone step on the brake pedal while we watched the truck from behind, we noticed that the passenger-side brake light was not illuminating. Continuing with the lighting test, we turned on the headlamps and noticed something even more interesting! When the headlamps were on, but the brake pedal was NOT depressed, the center high mounted stop lamp (CHMSL) or "3rd brake light" illuminated dimly. That's certainly not normal! Since we were already suspicious of the passenger-side brake light bulb, we decided to remove it. Upon removing the bulb, the 3rd brake light immediately went out, which is the expected behavior since the brake pedal was NOT being depressed. Looks like we found our problem.

Before we continue, we just wanted to add a note about vehicle brake light and indicator light systems. In the case of the 3rd gen Tacoma, the brake lights are also the tail lights, meaning they glow red when the tail/head light switch is on, and they glow much brighter when the brake pedal is depressed. The turn signals are separate from the brake lights and not a topic we are going to get into right now! However, the 3rd brake light should never illuminate at all unless the brake pedal is depressed. Knowing this, we immediately noticed something was off. Since removing that bulb immediately made the 3rd brake light turn off, we knew it was the culprit.

An autopsy of the passenger-side brake light bulb revealed that it was just a cheap LED bulb that had failed in such a way that there was low resistance between some of the pins, which caused a short to battery in the brake light circuit. This probably back-fed the brake switch circuit, causing the DTC code and scary warning message. The 3rd gen Tacoma tail lights are an all incandescent design from the factory, but some cheap LED bulbs were installed in place of the incandescent bulbs years ago. Moral of the story is, think twice before swapping in cheap LED bulbs in place of incandescent ones on a vehicle not originally designed for LED bulbs!

TL:DR a cheap LED brake light bulb failed (short), causing a brake switch circuit B high condition (short to battery), resulting in a brake override malfunction warning message on the instrument cluster. Replacing the failed bulb solved the problem.