I've got an ST170 and the engine management light comes on now and then. I just disconnect the battery for 30 mins it'll reset it, when I reconnect it just leave the car idling for about 10-15 mins, shouldn't cause any problems. Its common in ST170's for the light to come on due to unburnt fuel passing past the hego (lambda) sensor on the overrun. Has never caused me any problems before.