Main Relay (Computer/Fuel System): Description and Operation
CIRCUIT OPERATIONWhen the ignition switch is in the START or RUN position, it connects circuit A1 from fuse 3 in the Power Distribution Center (PDC) to circuit A21. Circuit A21 powers circuit F18 through fuse 9 in the fuse block. Circuit F18 supplies battery voltage to the coil side of the ASD relay. The Powertrain Control Module (PCM) provides the ground path for the coil side of the relay on circuit K51. Circuit K51 connects to cavity C3 of the PCM.
When the PCM grounds the ASD relay, the relay contacts close and connect circuit A16 from fuse 4 in the PDC to circuit A142. Circuit A142 splices to supply voltage to the fuel injectors, ignition coil, and heated oxygen sensors. Circuit A142 also connects to cavity C12 of the PCM.