there is no specific code chart for these systems like newer systems.
they do display warning or diagnostic codes by blinking the 'check engine' light.
When the key switch is turned on, the check engine light is illuminated to show that the lamp is operational. If the engine is not started, the light will turn off after 20 seconds. If error codes are detected (RPM=0), the light will begin to blink codes sequentially after an additional 15 seconds.

here are how they work:
key on
engine not running (RPM=0)

- lamp turns off after 30 seconds - no error codes
- after 45 seconds, lamp flashes - shows error codes
- lamp off - normal operation
- lamp blinks slowly - charging system problem
- lamp blinks quickly - overheat/over speed
- lamp on steady - other error detected

System Faults
- 3 flashes - Fuel System Error
- 4 flashes - Pedal Sensor open
- 6 flashes - Engine Temperature Sensor
- 8 flashes - Battery Voltage
- 9 flashes - TACH. (rpm input)

this is how it is explained in the check engine light blink faults in the troubleshooting manual.
There is no way to force it to blink codes, it is all handled in the ecm and if a fault is present it will display the code by blinking the light or staying on solid.

If you want more definitive diagnostic info then you may need to get the LS20/S15G software program and see what else it may show you.

i would first try removing the mixer cover and pulling the diaphragm and cleaning it and the mixer throat out, if it is dirty this can cause problems with starting and running.
- if the pedal sensor is out of range that can cause limp mode when engine is running but usually does not keep the engine from starting and running.
- if the 02 sensor is faulty the engine should start but when it senses a problem with it the engine will go into limp mode, but this does not keep engine from starting and running.
- if there is a problem in the throttle body this might cause the symptoms you are having, check the harness at the plug and where the harness enters the body.
- if the engine temp sensor is faulty one of 2 things can happen depending on the level of temp difference, it will either flash a code and go into limp mode, or it will flash, go into limp mode and then shut down after 45 seconds.
- if it detects a flywheel sensor (RPM TACH) fault the check engine light is illuminated, engine enters limp mode. If there is no signal from the flywheel sensor the fuel lockoff will not operate and engine will not start and run.

hope this helps