I sometimes get the engine management light (MIL) coming in, especially on a hot day, and it's always been P0404 'EGR Performance' and it always goes out again a few days later, but just in case the light is for something else, I bought a Sealey VS8700 for about forty quid from a local car-parts shop, and it does an awful lot more than I actually understand, so I've never used it to its full potential. It doesn't just give the fault code - it tells you what the code means as well. It'll read and delete codes, which is all I've used it for. It'll 'View Freeze-Frame Data' and it'll 'Retrieve I/M Readiness Data' which I read is something about emission systems.

I think that the police should carry one of these, because it'll read the VIN code number. You see those 'reality' police programmes on the telly, where they find a stolen car with false number plates and possibly false VIN codes - they only need to plug one of these in and they could read the VIN off the engine computer and compare it to whats showing on the car.

I have Torque Pro app on my phone. Coupled up to a 20 quid OBDII bluetooth adaptor I'm well chuffed with it. The Pro is about 3 quid, but I think even the free version does code reading.