rob davey said:I had this on mine; mine misfired once and never again and that put the light on. The light stays on until it gets reset at the stealers and they print off the fault, often costing £90 for cock all.
Andy said:for reference you can get a code reader for £27 on Amazon, I've posted a list of fault codes in the How-to section.
One off codes and it's not worth it, if you've got something persistent I'd get one.
Andy said:http://www.amazon.co.uk/ELM327-Based-Diagnostic-System-OBDII/dp/B001C1QQJA/ref=sr_1_1?ie=UTF8&s=electronics&qid=1251897946&sr=8-1
does the job fine, if you can mess about with usb-serial ports and all that ( i had a pig to get it to talk, usual programs "watching" the port which needed to be turned off first )
comes with freeware software to read codes and reset EMLs.
Bought mine as my other car is OBDII as well. There's cheaper ones on Amazon too, but I liked that one.