ECM "Ed99" Data Code
WARNING: This page is about a different car, the 1988 Cadillac Seville and 1988 Cadillac Eldorado. However, it is still accessible from the selected car via links, so may be relevant.
The ECM Programmable Read-Only Memory (PROM) identification number is displayed as a number up to 3 digits long which can be used to verify that proper PROM is installed in ECM.