You're seeing a response from the lamp check module which checks only resistance in the circuit-which is why you can't even use non-nickle based bulbs in the rest of the system. It's set to monitor the resistance from the old halogen bulb,which would be quite different from the xenon setup. maybe setting up a separate resistor from the line to the module-or maybe one of the manufacturers of the new xenon aftermarket systems have a plug in solution.........