ABS INOP Light is on because of third brake light?
LED's don't need or pull the power that incandescant(sp?) bulbs require, threfor if you replace something that had a regular bulb with something that uses LED's you need to also add additional resistance tot he circut so other things that monitor or work with them work properly.
Shoebox had a good idea of useing the resistance in a 12V relay coil, but this can also be done by getting the proper size resister and wireing it in parallel as shown in shoebox's diagram. This masks the amount of ressitance being pulled to make the system think it has regular bulbs in there.
All you need to actually do, is wire it up somewhere in the circut leading to the LED harness, Shoebox has colors listed of what goes to the LED's but it can be done anywhere in the circut and probably the best place is behind the interior panel that the rear seat speakers are in on the driver side. You will see the wires going up there that head out to the brake light eventually and can put the relay (or resister) there so the rest of the wiring is untouched and you don't have the relay rattling around in the hatch.




