I wrote all the steps for diagnosing a code 4 (crank sensor fault) below and accidentally answered my own question in doing so. I don't want to delete it after all my efforts so I'm add a few things and leave it here in case anyone happens to find it when searching or whatever. Hope this helps someone in the future This is from alldata. Not 100 percent identical word for word, but steps are still exactly the same.

-Pull HAZARD fuse for at least 10 seconds and retest. Does code return? If yes, proceed.

-Disconnect 6P connector from the TDC/CRANK sensor. Measure resistance between terminals D and E (there should be 2 pins then a blank slot on the bottom row. Right next to the blank slot is D and next to that is E). is there 350-550 ohms? If so, proceed. If no, replace distributor.

-Check for continuity to body ground on terminals D and E individually. does continuity exist? If no, proceed. If yes, replace distributor.

-Reconnect connector. Connect PGM-FI test harness only to main harness, not to ecu (I used paperclips to backprobe appropriate terminals and made sure they didn't accidentally touch). Measure resistance between B10 and B12. is there 350-550 ohms? If yes, proceed. If no, repair open in orange and/or white wires.

-Check for continuity to body ground on B10 terminal. Does continuity exist? If yes, repair short to ground in orange wire. If no, substitute a known good ECU if problem goes away, original ECU is at fault.

Hope this helps someone, it should have everything you need to diagnose the code 4 issue. This is for 86-88 integras. Tests should be extremely similar if not the same for other obd0 4 cylinder hondas, but don't take my word for it. Enjoy.