Principles of Operation: Notes

WARNING: This page is about a different car, the 2010 Mercury Mariner and 2010 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.

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 signals on multiple circuits to the headlamp switch. There is one circuit for each headlamp switch position. At any given time, one of the signal circuits is switched to ground.

If the SJB does not detect any of the inputs to the headlamp switch are active (switched 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).

Additionally, if the SJB detects multiple circuits short to ground, the SJB implements a planned strategy depending on the multiple inputs received. Based on the multiple inputs received, the autolamps, the headlamps and/or parking lamps are turned on.

If either situation occurs, the SJB cannot 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 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 is routed to ground.

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.