For 1990-2009 cars

All grounds, in-line connectors, and splices have identifying numbers that correspond to where they are located in the vehicle. The following table explains the numbering system.

Callout Numbers | Zone Description
--- | ---
100-199 | Engine compartment (All forward of the dash panel)
200-299 | Within the instrument panel area
300-399 | Passenger compartment (From instrument panel to the rear of the passenger area)
400-499 | Luggage compartment (From the rear of the passenger area to the rear of the vehicle)
500-599 | Within the driver door
600-699 | Within the front passenger door
700-799 | Within the left rear door
800-899 | Within the right rear door
900-999 | Within the liftgate, endgate, or rear compartment lid