Here's a step-by-step for you. This only works on OBD1 vehicles.
-Sit in the driver's seat.
-Turn the ignition to the On position, but do not start the engine
. On position means all lights should illuminate in the cluster.
-Immediately depress the accelerator fully and release fully 5 times quickly.
-Wait for a few seconds and you will see the Check Engine light flash once, then start it will start to blink.
-All codes are comprised of 4 digits. The number of blinks corresponds to the fault code. For example, ON then pause, ON ON then pause, ON ON ON ON then pause, ON ON ON then off would be a 1243.
-Each four digit code will be flashed sequentially. When the codes start to repeat, all stored codes have been displayed.
-Turn the ignition off and check the codes with the table below. 1444 and 2444 means no problem and that is what you hope to find! Good luck!
Here's the chart with the codes: http://www.bimmerzone.com/fcodes.htm
Edited by Kellie on 10/5/2009 at 1:30 PM EST