Pull down the passengers side carpet from the passengers footwell to reveal the ECU. There should be a small window on the top center of the ECU with an LED. If the LED is flashing, this means that there is some type of system failure. Check the flashes to find out the code.
To figure out what code is flashing, just count the blinks.
Here is a list to show what each of the codes means.
0 - Faulty ECU
1 - Oxygen Content
3 - Manifold Absolute Pressure
4 - Crank Angle
5 - Manifold Absolute Pressure
6 - Coolent Temperature
7 - Throttle Angle
8 - TDC Position
9 - #1 Cyl. Position (HF and Si Models)
10 - Intake Air Temperature
12 - Exhaust and Gas Recirculation System
13 - Atmospheric Pressure
14 - Electric Air Control
15 - Ignition Output Signal
16 - Fuel Injector
17 - Vehicle Speed Sensor
19 - Lock-up Control Solenoid Valve
20 - Electric Load
