Circuit Description

The ignition 1 relay is a normally open relay. The relay armature is held in the open position by spring tension. Battery positive voltage is supplied directly to the relay coil and the armature 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 module. When the ECM commands the relay ON, ignition 1 voltage is supplied to the ECM through the ETC fuse in the underhood fuse block. This ignition 1 voltage input to the ECM provides the ignition power for the electronic throttle control (ETC) circuitry, and is also used to confirm that the ignition 1 relay has closed. A voltage more than 10 volts indicates a short to battery positive voltage in the ignition 1 voltage circuit to the ECM. This DTC will set when the ECM detects more than 10 volts on the ignition 1 voltage circuit to the ECM, after the ignition switch is turned OFF.