CB400X LED Aux Brake Light Installation

Safety has no compromise. In my recent 2,000km tour to Thailand, I experienced one of the heaviest downpours when traveling along the Malaysian North-South Highway (NSHW). Visibility was so bad that many vehicles had their hazard lights blinking as the crept along. I had a riding buddy close behind me, and over the Sena Bluetooth comms, I queried…

“Hey JC, I’m gonna lightly hit my brakes. With my tail lights turned on, can you help me take a look to see if the OEM Honda CB400X brake lights are obvious enough, or do you think I should add an auxiliary brake light?”

I tapped on the brakes lightly and intermittently.

“You should add an additional brake light.”

The CB400X brake light connector.

The CB400X brake light wires and connector can be accessed from the LHS of the bike underneath the seat. While I haven’t figured out what the other connectors are, I’ve traced the brake lights to the right-most connector (it was the only 3-wire connector anyway).

The brake light connector removed.

To test if it was the correct connector, I gently disconnected it and turned the ignition on. True enough – the brake lights went dead.

The 3-wire brake light connector. Green, Green-Yellow, and Purple-Blue
The CB400X / CB500X brake / tail light wiring diagram.

The brake / tail light has 3 wires. The GREEN wire is GROUND, GREEN-YELLOW is for the BRAKE light, and PURPLE-BLUE wire for TAIL light. For the purpose of this exercise, I tapped on the GREEN and GREEN-YELLOW wires for the aux LED brake light.

The simple LED strip brake light kit.
LED brake light installed.
Tail light ON – no brakes.
Tail light AND brake light ON.
Success! LED auxiliary brake lights installed on my CB400X.

Viola! LED brake lights installed! This will definitely give better braking visibility to vehicles following behind.

8 thoughts on “CB400X LED Aux Brake Light Installation”

  1. Awesome idea, but how about when the top box is on?

    I was thinking of adding a light that stays on instead, like a rear fog light function.

    1. The top box won’t cover the LED’s. It’s approximately at eye-level of a motorcar driver. Trucks and other taller vehicles *may* have a little trouble viewing it when it’s (far, far) too near, but one should NEVER get that near a truck anyway…

    1. Hey Zed I have just discovered that the GREEN/BLUE wire on the OPTION connector supplies 12V when the brakes are activated! This is a better way to access the brake signal than splicing the original cables.

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