Honda CR-Z Center High-Mount Brake Light (CHMSL) Flasher Install

The module is about the size of a quarter and carries 37 selectable patterns, one of which disables flashing altogether. Its circuit board is sealed in plastic, so contact with the metal hatch, condensation, or moisture will not harm it. Check the two white programming leads first: some units ship with these already cut into two separate tails, while others arrive with an intact loop. If yours is looped, cut through the middle of that white loop now so you have two independent programming leads to work with later.

Climb into the rear cargo area. Using a trim tool or flat screwdriver, release the horizontal plastic cap that runs between the upper and lower panes of rear glass. Begin prying at the small recess on its passenger-side lower edge, separate it from the neighbouring trim, then draw the panel toward you; it is held by side tabs and by three push clips into the hatch metal. At the driver-side end, lift it away from the adjoining panel deliberately, or you may accidentally pop off the separate cover that shields the wiper motor instead.

With the cap removed, find the green connector; it sits on the exposed hatch metal toward the driver's side. Slide it upward out of its white retaining clip, leaving the clip mounted on the car, then separate the two connector halves. Leaving the battery connected is fine here: you are downstream of the brake switch and can simply unplug this connector while you work, so the risk to the car's electrics is minimal, and you will need the brake circuit live to test and program the module.

Slide back the loose black sheathing around the wiring to open up some working room, then either trim it off or tape it out of the way. Identify the positive conductor, which is white with a black stripe, and cut it. Place the cut a little farther from the plug than seems necessary so the finished splices can be tucked into the recessed slot in the hatch. Work carefully here, because the defogger grid and glass are close and a slipped tool can damage the grid.

You now have two ends of the white feed wire. Join the plug-side end to the module's red wire using a supplied butt splice. Connect the module's black wire to the vehicle's black ground wire with the supplied tap splice. Leave the module's yellow output lead disconnected for the moment so you can power-test the module before committing the final splice.

Reconnect the green connector, then have a helper press the brake pedal. The module's onboard green LED should light up, confirming it is receiving power. Do not skip reconnecting the plug first, or the test will show nothing. Only proceed once the LED responds to the brake pedal.

Unplug the green connector again. Splice the module's yellow output lead to the remaining, lamp-side end of the white wire using the last supplied butt connector. Reconnect the green connector and seat it back into its white clip. With a helper on the brake pedal you can now watch the lamp run its default pattern.

With a helper holding the brake pedal down, briefly touch the two white programming leads together. Each touch steps to the next of the 37 patterns and wraps back to the first after number 37. The patterns differ in flash speed (fast, medium, or slow) and in re-activation delay (0, 15, or 30 seconds before the lamp will flash again). A non-zero delay stops the light from pulsing over and over in stop-and-go traffic, which is less irritating to drivers behind you. Pattern 37 is the off setting, leaving a normal steady lamp. Note that some of the most aggressive strobe patterns can shorten the life of an LED lamp.

Once you have settled on a pattern, tape over the bare ends of the two programming leads to insulate them. Tape the new wiring to the hatch metal and feed as much of it as you can into the hatch slot so it clears the trim on reassembly. Refit the trim cap in the reverse order of removal; it snaps back into place easily. Test the brakes one more time before closing up.