Main Relay (Amigo, Rodeo, Trooper & VehiCROSS)
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2000 Isuzu VehiCROSS, 2000 Isuzu Trooper, 2000 Isuzu Rodeo, 2000 Isuzu Hombre, and 2000 Isuzu Amigo. However, it is still accessible from the selected car via links, so may be relevant.
This 4-terminal relay is located in under-hood fuse box. Main relay is used for PCM power control. See appropriate wiring diagram in WIRING DIAGRAMS article for terminal identification.