Relay Box (Interior) Description and Operation

Description

1. 1
   General Functions: Internal junction box + some BCM functions. It uses CAN communication and IPS to control loads.
2. 2
   Main Functions:

   • Low-speed CAN communication (100 kbit/s)
   • Self-diagnosis (lamp open/short circuit)
   • Fail-safe (if MCU/CAN fails, headlamp/tail lamp operates directly)
   • Lamp overvoltage protection (PWM function)
   • Overload and short-circuit cut-off function: PCL (Programmable Current Limit)

   

3. 3
   Description: A system that automatically cuts power supplied to loads to reduce unnecessary dark current consumption depending on vehicle condition.

   

4. 4
   The SJB has 3 modes: "Normal Mode", "Sleep Mode" and "Power Down Mode". The automatic dark current cut function operates in "Sleep Mode".

   • "Sleep" condition: Ignition OFF, constant input switch, CAN network not active.
   • Sleep cancellation conditions: any input switch, CAN network activation, KEY ON, IGN ON.
   • "Power Down" condition: When the preset timer used to cut load power expires.
   • "Normal Mode": The SJB function is normally active.
   • "Sleep Mode": This low-power mode is activated to reduce SJB or BCM power consumption. The automatic dark current cut function activates.
   • "Power Down Mode": Power to the microcontroller and circuit loop is cut to minimize power consumption. Operation stops.
5. 5
   Description - Automatic Dark Current Cut-off

   

   Before Delivery to Customer	Fuse switch OFF.
   • All doors closed and RKE door locked, or constant switch status (automatic dark current cut scenario starts). - After 20 minutes in "Sleep" condition - SJB power down (SJB dark current: 200 µA) and body/wake-up lamp load power cut-off
   After Delivery to Customer	Fuse switch ON.
   • All doors closed and constant switch status: C_BAState=OFF (automatic dark current cut scenario starts.) - After 20 minutes in "Sleep" condition - SJB power down (SJB dark current: 200 µA) and lamp load power cut-off • In case of RKE lock: C_BAState=ON & Trunk SW=CLOSE (automatic dark current cut scenario starts.) - After 35-65 s in "Sleep" condition (other device wait time: 30-60 s + SJB sleep mode considered 5 s) - SJB power down (SJB dark current: 200 µA) and lamp load power cut-off

6. 6
   Incorrect switch setting problem: If the fuse switch is set to OFF (before delivery to the customer) by the customer or a technician, and the automatic dark current cut function is activated, the following problems may occur.

   Symptom	Related Part
   • Door lock/unlock and trunk opening are not activated by RKE. (Wake-up for each module is not activated.)	BCM
   • Digital clock reset. (Memory reset.)	Digital Clock
   • Audio setting values (volume, frequency) are reset. (Memory reset.)	Audio

   
   * If the fuse switch is set to OFF (before delivery to the customer), power to the BCM, digital clock and audio is cut off.