The ECU outputs a diagnostic code whenever the "Check Engine" light is lit. For 1G owners, you can:
- use a Chrysler scan tool to read the code. Not an option for most people, but still.....
- use a multimeter to read the code, as described in the shop manual, or as in this post by an early club member.
- use an LED to read the code, as described in this post by another club member, and this post from December 1998. The December post also details many of the output codes.
- use a buzzer to read the code, as described at the Diagnostic Engine Codes and Procedure page. This page also has a list of many of the codes.
2G turbo owners need an OBD tool to read the ECU codes. Non-turbo owners can cycle the ignition key on-off-on-off-on, and the "Check Engine" light will blink out the codes. For NT owners, the codes are the same as a Neon. For the meaning of the codes, check the Digest archives, look in a shop manual, or check out this link from the 2G non-turbo pages.
Lots of 2G turbo owners mistakenly try to cycle the ignition key to get the 'Check Engine' light to blink out the codes. It doesn't work on Mitsubishi engines - only Chrysler engines. 2G NT cars have 420A Chrysler engines very similar to the Neon cars, while 2G T cars have 4G63 Mitsubishi engines similar to 1G cars. For this reason the codes are also different between 2G turbo and non-turbo cars.
Check this section of the Club DSM Homepage [Technical Difficulties/ECU Problems/Error Code Readers] for more information.