My son has a 1993 Honda accord with an intermittent code 15. When the check engine light comes on the car will not start or run. If you let the car sit for awhile, the check engine light goes out and the car will start and run again. Could someone please tell me how to diagnose the problem without a lot of specialized equipment. Thank you.

Read sections A and B:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-honda-civics-46563.html

Code 15 (Ignition Output Signal circuit) could be an indication that the Ignition Control Module (igniter) has failed.