Principles of Operation

PRINCIPLES OF OPERATION

NOTE: The smart junction box (SJB) is also known as the generic electronic module (GEM).

The SJB monitors the headlamp switch position by sending voltage reference signals on multiple circuits to the headlamp switch. At any given time, one of the signal circuits is routed to ground. If the SJB does not detect any of the inputs to the headlamp switch is active (routed to ground) for 5 seconds, the SJB turns on the exterior lights and keeps them on for 10 minutes after the ignition switch is turned off (or 10 minutes from the time the SJB does not detect any headlamp switch input if the ignition switch was already off). If the SJB detects multiple circuits short to ground, the SJB implements a planned strategy depending on the inputs received. If either of these situations occur, the SJB should NOT be ruled immediately as being at fault. This is normal behavior of the SJB design as it has detected a fault with the inputs from the headlamp switch.

The SJB also monitors the multifunction switch for a flash-to-pass or high beam request. There are 2 voltage reference circuits which monitor this. When the multifunction switch is in the FLASH-TO-PASS or HIGH BEAM position, the voltage signal for that input is routed to ground.

NOTE: The flash-to-pass feature does not require any input from the headlamp switch.

When the SJB receives an input requesting the headlamps on, the SJB supplies voltage to the low beams. If the low beams are on and the SJB receives a request for high beams (or a flash-to-pass request), the SJB energizes an internal relay which routes voltage to the headlamps.

Headlamp Functionality - Halogen
When the low beams are requested (based on inputs to the SJB), the SJB provides voltage to the low beams.

When the high beams are requested, the SJB energizes an internal relay which routes voltage to the high beams and terminates voltage to the low beams.

When the flash-to-pass feature is requested, the SJB energizes an internal high beam relay which routes voltage to the high beams as long as the multifunction switch is held in the FLASH-TO-PASS position.

Headlamp Functionality - High Intensity Discharge (HID)
Relays are utilized to control the voltage to the HID ballasts. The ballasts are located on the side of each headlamp assembly.

When the low beams are requested (based on inputs to the SJB), the HID relays are energized and voltage is routed to the HID ballasts to illuminate the HID bulbs.

When the high beams are requested, the HID relays stay energized and the SJB energizes an internal high beam relay which routes voltage to the headlamps to actuate a shutter located within each headlamp. This changes the headlamp beam pattern to illuminate a greater distance.

The flash-to-pass feature is unique for HID equipped vehicles. If the low beams are off when the flash-to-pass is requested, the SJB provides voltage to the HID relays and energizes the internal high beam relay for the shutters within the headlamps for less than 0.5 second. If the SJB is already providing voltage to the HID relays (low beams) when the flash-to-pass is requested, the SJB energizes the internal high beam relay as long as the multifunction switch is held in the FLASH-TO-PASS position.