Not really had a play with the software yet. Just done the basic stuff like reading codes and resetting them. I reset all the codes again last night and drove 15 miles to work today and the engine management light has not come back on yet.
Whatever is causing it to come on is obviously taking some time to diagnose a fault. initially I was thinking of oxygen sensors as these generally do take a while to decide that there is a fault and come on. if it were something serious then I would expect the engine management light to come on again straight away.
just found this excellent description of how the oxygen sensors work
"The fuel/air mixture is calculated from measurements made (primarily) from the Mass Airflow Meters (MAF's) and the air-intake temperature. These measurements are used to set the injector duration from a set of tables held in the computers. To get the mixture exactly right there are Lambda sensors in each exhaust that samples the Oxygen level to fine-tune the injector duration (and hence the correct fuel/air mixture). The adjustment that the Lambda sensors can demand is called the Adaptations. These adjustments are limited and once this limit is reached the OBD light will illuminate and error codes stored. If the adaptations have reached their limits it means that there is some problem with the ability to produce the correct fuel/air mixture. This can be due to bad measurements (air temperature, poor MAF reading) or it could be due to an air-leak which will make the mixture too lean."
this is very interesting as I had the two error codes
#28= Additive Adaption Bank 1 Control Reached
#29= Additive Adaption Bank 2 Control Reached
E90 318i 2007 N46 2.0 Manual
E53 X5 2004 M54 3.0 Sport Auto
E83 X3 2004 M54 2.5 Auto
Last edited by white_lancer; 10-25-2012 at 12:30 AM.