DTC P1623: Prom Error
WARNING: This page is about a different car, the 1995 Pontiac Bonneville, 1995 Oldsmobile Eighty-Eight, and 1995 Buick LeSabre. However, it is still accessible from the selected car via links, so may be relevant.
Ensure PROM is correctly inserted in PCM socket. If okay, replace PROM, clear memory and recheck. If Code P1623 reappears, replace PCM.
NOTE:
To prevent possible electrostatic discharge damage to PCM or PROM, DO NOT
touch component leads. DO NOT
remove integrated circuit from carrier.