Main Relay (Computer/Fuel System): Description and Operation

CIRCUIT OPERATION
The Automatic Shut Down (ASD) relay is located on the front of the right toe box. Power for the coil side of the ASD relay is supplied on circuit F12. This circuit is HOT when the ignition switch is in the START or RUN position and protected by a 20 Amp fuse located in cavity 1 of the fuse block.

Ground for the coil side of the relay is controlled by the Powertrain Control Module (PCM) on circuit K51. This circuit connects to cavity 3 of the PCM.

Power for the contact side of the relay is supplied on circuit A14. This circuit is HOT at all times and protected by a fusible link located near the auxiliary jumper post on the left toe box.

When the relay is energized, the contacts in the relay CLOSE connecting circuits A14 and A142. The A142 circuit supplies power to the fuel injectors, heated oxygen sensors, ignition coils, generator, and a ASD relay energized signal to the PCM.