I've just looked at a good site

Chris,

If you've got a fault, the engine check light on the dash will be on.

To find out what the fault is:

1. switch off ignition
2. connect the black or brown plugs under the dash
3. turn on ignition
4. the check engine light will flash at you. Long flashes are 10s, short are 1s, (e.g. 44 is four long, four short). If you've got more than one fault another number will flash at you, other wise the same no. will repeat.
5. turn off ignition
6. disconnect plugs.

Steve.