Hi,

Sierra Cosworth has next ECU:s
-Engine ECU, (has red or green sticker. Color depend what engine model your car has, YBG has green) location behind glove box
-ABS ECU, (2 different models, 2wd or 4wd, 4wd model has yellow sticker on it what has 4x4 text) location behind glove box
-Alarm ECU, (not sure are the all same) location behind dashboard
-Warning light ECU, (not sure are the all same) location not sure
-Bulb voltage ECU (has light red sticker on it) (not sure are the all same), deliver information to warning light ECU, location driver side

In the attached picture you have there warning light ECU.