The ground circuit to the Accessory Control Relay is switched by the body control module (BCM) to control the relay when the ignition is turned to accessories or turned on.

When the relay is energized, power is supplied to the radio, windscreen wiper systems and other accessories, if fitted. There are two options for disabling the accessory power:

The shut down options can be selected using the MFD or scan tool. The default option is set to Door Open. However, if the radio is switched on after disabling the accessory power, the BCM will energize the Accessory Control Relay for a period of 63 minutes. The Accessory Control Relay is switched off immediately if the radio is switched off within this time frame.

If the intermittent wiper system is in operation after the accessory power is disabled by the BCM, the Accessory Control Relay will be disabled by the BCM when the wiper park signal is sensed. If the wiper park signal is not sensed within 3 seconds, the BCM will automatically disable the relay.

When the ignition switch is turned to Accessories or to ON, a 12-volt supply from the ignition switch is detected by the body control module (BCM). The BCM provides a ground connection to the Accessory Control Relay . This causes the relay contacts to close, supplying 12 volts to the BCM accessory circuits. The BCM disables the Accessory Control Relay when 0 volt is detected at the BCM or when the driver door is opened. Opening of the driver door closes the Driver Door Ajar switch contacts, pulling the signal at the BCM low.

If the front wiper is in operation after disabling of the accessory power is initiated, the BCM will monitor the Wiper Park input. When 12 volts is detected at the Accessory Control Relay is then disabled. If the wiper park signal is not detected within 3 seconds, the BCM will automatically disable the relay.