I had the same problem with mine and it was the door sensors that were dirty, I took the sensor apart on both sides and wire brushed the contacts on them and on the light unit itself and has been working fine for over a year now :rockon:
http://www.ukstarletowners.com/topic/75586-glanza-engine-4efte/?view=getnewpost . Then use your head then perfect running engine and I'll give you hand mate if you need it?
Alrite mate its ben, heard bout what happened :( but try this chap http://www.ukstarletowners.com/topic/75722-99-black-glanza-v-breaking/?view=getnewpost