You may have the early ECU [ before 3/93]
Slightly different procedure

To get codes hold for 2-4 secs
After code comes up , wait 2 secs and then clear it by holding 5-6 secs.
Do them all until you get a single flash... You have to do each and every one individually.
If you don't get the single flash, you haVE NOT CLEARED THE CODE , SO TRY AGaiN

aFTER YOU GET 1 FLASH [ NO CODES STORED] only then CAN YOU RESET/ACTIVATE THE ecu MEMORY.
THAT IS done by HOLDING 6-8 SECS after A 1 APPEARS . tHEN YOU TURN KEY OFF 2 SECS [ OR A LITTLE MORE ] , BACK ON FOR AT LEAST 10 AND START THE CAR.
yOU SHOULD NOW HAVE NO CODES AnD A NEW , RESET ECU ...

forget the caps... i hit it by mistake and don't want to do it again...