Find your ECU
It's hiding behind the kick panel down by the driver's feet (LHD models)
Take off the cover, undo the 12mm bolts holding it in place.
Take a jeweller's screwdriver (the little ones) and you'll find a little hole with a slotted screw inside it. Turn that screw fully clockwise until you hear a click.
Watch the 2 LEDs. They will flash together 1-1-2-1-3-1-4-1-5 and start over.
As soon as it flashes 3 times, turn the screw all the way back counterclockwise. This will lock you in the "self diagnosis" mode
The LEDs will now flash at you. The first number of flashes represents the first digit (tens), the second, the second(ones).
And this is the breakdown of the codes it will give you
11 Crank angle sensor
12 Air flow meter
13 Water temp sensor
14 Car idle sensor
21 Ignition signal
22 Fuel Pump
23 Idle Switch
24 Overdrive switch (Autos only)
31 Air Con (Or no fault on cars without Air con)
32 Start Signal
34 Detonation Sensor
44 No Fault
By no means is this fool proof, but it's usually a good starting point.
