Relays Controlled By The BCM

Low beam relay 

The lowbeam switch is a direct input to the BCM. The lowbeam lamp relay is then powered through low side control of the BCM. This circuit is electronically controlled and continuously monitored for malfunctions.

Accessory relay 

The accessory relay works in conjunction with the BCM's power accessory delay feature to control the operation of the radio and power outlet. The accessory relay is turned on through high side control on the BCM. This circuit is electronically controlled and continuously monitored for malfunctions. Depending on the ignition switch position, the accessory relay will remain on or will time-out and turn off. The accessory relay remains on in the RUN and ACCY positions of the ignition switch. In the UNLOCK and OFF positions, the relay will remain energized for 120 seconds then turn off. During this time-out period, if the driver door is opened and the ignition key is removed, the relay will turn off immediately. While the ignition switch is in RUN and the clutch and START button is pressed (and not ignored), the relay will also drop-out, then resume operation. Accessory relay operation is most noticeable by observing the operation of the radio. Both Driver and passenger windows will work during accessory delay. NOTE: The windows cannot be driven up during accessory delay if the door is ajar. NOTE: A faulted ignition switch will cancel delay. 

Passenger Window Relays 

There are two relays controlling the Up & Down function of the Power windows. The BCM controls the window Up relay coil with a High side driver. This driver has Short Current diagnostics. The BCM controls the Down relay coil with a Low side driver. This driver has Open, Short to ground or Short to Voltage diagnostics.

Horn relay 

The horn relay operates through a direct wire input to the BCM from the horn switch. The relay responds to the horn switch, remote door lock and VTSS alarm functions. The horn relay coil is controlled by the BCM. Under normal operating conditions, if the horn is pressed for longer than 30 seconds, the BCM will automatically deactivate the horn to prevent damage to it. The BCM will reactivate control of the relay after a 25 second cool-down period. This circuit is electronically controlled and continuously monitored for malfunctions.

Front blower relay 

The BCM powers the blower relay in ignition RUN. The PDC powers the blower motor through the closed relay contacts. To govern Low, Ml & M2 blower speeds, current flows from the blower motor through the blower resistor. For High speed, current flows from the blower motor to the A/C-Heater Control to allow for blower operation should the resistor fail. The ground path is supplied through the A/C-Heater Control.

Rear Window Defogger (EBL) relay 

The rear defrost switch is part of the A/C-Heater Control Module (Manual Temp). When the ignition switch is in the RUN position and the rear defrost switch is turned on, the A/C-Heater Control Module controls the relay. The BCM Controls the fused ignition switch output circuit to the EBL relay coil. The relay provides voltage to the rear window defrost grid, and ground is attached to the vehicle body. The relay will only allow the rear defrost to operate in the RUN position. This circuit is electronically controlled and continuously monitored for malfunctions.