Principles of Operation

Parking, Rear and License Plate Lamps

Principles of Operation

NOTE: The Smart Junction Box (SJB) is also known as the Generic Electronic Module (GEM).

The SJB (Smart Junction Box) 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 (Smart Junction Box) does not detect any of the inputs to the headlamp switch is active (switched to ground) for 5 seconds, the SJB (Smart Junction Box) turns on the parking lamps and headlamps and keeps them on until the battery saver feature times out.

Additionally, if the SJB (Smart Junction Box) detects multiple headlamp switch input circuits short to ground, the SJB (Smart Junction Box) turns on the parking lamps and headlamps and keeps them on until the battery saver feature times out.

Refer to Exterior Lighting Exterior Lighting for information regarding the battery saver feature.

If either of the above situations occur, the SJB (Smart Junction Box) cannot be ruled immediately as being at fault. This is normal behavior of the SJB (Smart Junction Box) design as it has detected a fault with the inputs from the headlamp switch.

When the SJB (Smart Junction Box) receives an input from the headlamp switch indicating a request for the parking lamps, the SJB (Smart Junction Box) energizes the parking lamp relay (internal to the SJB (Smart Junction Box)), which supplies voltage to the exterior lamps.