In 1990, OBDI was still in use, not OBDII. OBDI did not have a standardized connector. You will probably need to activate the SCS mode of the PGM-FI and count flashes of LEDs on the PGM-FI module under the seat to get codes.
the 1994 Honda accord has an obd2 ecu.
Answering "How can you diagnose a 1998 Honda accord without an OBD scanner?"
The 1996 Honda Accord OBD 2 port is inside storage behind ashtray
The 1996 Honda Accord OBD 2 port is inside storage behind ashtray
The OBD port on a 2002 Honda Accord is located on the engine. There are other vehicles that have it on driver side of the dashboard.
The 1998 Honda Accord OBD 2 port is under driver side dash above kick panel
The 2003 Honda Accord OBD 2 port is under driver side dash above dead pedal
where is the plug to conect the code reader on a 1990 Honda accord
The 1997 Honda Accord OBD 2 port is inside storage behind ashtray
The 2006 Honda Accord OBD 2 port is under driver side dash next to kick panel
The 2005 Honda Accord OBD 2 port is under driver side dash above the kick panel
location of obd port for a 2002 2 door Honda accord