Steering Wheel Switches The steering wheel switches, SET+ and RES, are non latching push switches that engage and disengage cruise control and adjust the set speed. While pressed, the switches supply a serial data stream to the ECM to adjust the set speed. ECM The ECM receives serial data from the steering wheel switches, which are interpreted by the ECM to operate cruise control. The ECM also controls the output of a cruise engaged signal to the EAT ECU. The ECM incorporates a software module and associated components to enable cruise control operation by direct control of the electric throttle. In addition to controlling the throttle, the software module monitors hardwired and CAN bus inputs to the ECM and prevents or suspends cruise control operation when the vehicle is not in the correct driving configuration While the master switch is selected off, only the OFF message can be transmitted. When the master switch is selected on, the power feed from the switch enables the interface switches to send either the SET or RESUME messages, depending on the inputs from the steering wheel switches and the cruise control status message from the CAN bus. When the master switch is first switched on, the output of the RESUME message is automatically inhibited until after the first engagement of cruise control. When cruise control is engaged, the ECM outputs a signal on CAN to the EAT ECU to provide a cruise control engaged signal. The EAT ECU uses the signal to switch between normal and cruise control modes of operation.