and ripped straight from car bible sight:
You might have seen websites and automotive shops stocking LED replacement bulbs for cars and motorbikes. Basically its a cluster of 19 or 24 LEDS (light emitting diodes) in a housing with a regular push-fit or bayonet plug on the back. The idea is that if you want brighter lights, you can replace your tail or turn lights with these LED replacements. There is a gotcha though that the manufacturers often hide in the smallest of small print. A lot of cars nowadays have onboard diagnostics which include a light check. Some of these use resistance to figure out if a bulb has blown. LED clusters have a radically different resistance to a filament bulb and its possible that when you replace your bulbs with LED versions, your car will continuously tell you that one or more bulbs is burned out. Getting one step more severe, if you use LED turn bulbs, your indicators could flash quicker or slower than you're used to. And the worst case scenario - some motorbikes have very tightly regulated voltages in their ABS systems and taking the filament bulb out of the brake light to replace it with an LED bulb can cause ABS errors and theoretically, an ABS shutdown. Granted thats worst-case scenario, but it is a possibility. So now you know.
http://www.carbibles.com/brake_bible.html
the thing about the bike abs could easily apply to car brakes...