Help my check engine light

[nissan240sx31]

Ok so my check engine light came on and i have an obd1 and so i checked it and it gave me the code 72 which is the three way catalyst system so i reset it and and when to work the next day and it came back on at about 15miles. so i get off work checked it and reset it again got back on home it didnt come back on. ive notice when i turn the key to start the check engine doesnt show up with all the rest of the lights. i rode around for about 5 mins and the check engine light came on for like 3sec went of and blinked about twice and it never came back on and so i stopped checked and reset it again. ive been riding around trying to get my check engine light to throw the 72 code again and it hasnt and my check engine light wont come on when i turn it to start whats going on if anyone knows what is going on please help me. the only time it will come on is if i do the diagnostic or when it comes on random and blinks for like 3sec

[w0nderbr3ad]

Don't know if this may help, but check all your o2 sensor or any sensors near your catalytic converters and see if any of them are loose or chewed up. I don't have an s14 but just an idea. Maybe somone with an s14 can provide better insight.