Circuit/System Description

The engine controls (EC) ignition relay, or PT relay is a normally open relay. The relay switch is held in the open position by spring tension. Battery positive voltage is supplied directly to the relay coil and the switch contact at all times. The engine control module (ECM) supplies the ground path to the relay coil control circuit via an internal integrated circuit called an output driver. When the ECM commands the PT relay ON, ignition 1 voltage is supplied to the following fuses in the underhood fuse block:

• The ETC Fuse
• The ELEK IGN Fuse
• The FUEL INJ Fuse
• O2 SSR Fuse
• EMISSION Fuse

The ignition 1 voltage that is supplied to the ECM through the ETC or PT relay fuse, provides power to the internal ECM circuits associated with the throttle actuator control (TAC) operation.