How-To: Check ECU Codes

This is for the self diagnostic only, mode III if you're counting

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.

http://img.photobucket.com/albums/v228/mr200/200sx/interior.jpg

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.

It should be noted that these codes very by year and engine. On my '88 SE, when you are changing the modes, the red and the green LED's flash together 1-2-3-4-5, with no 1 in between. The codes are also different, I don't have them in front of me, but on mine 55 = no codes, not 44.