Body Control Module

BODY CONTROL MODULE
The KJ Body Control Module (BCM) is attached to the Junction Block (JB), which is the interface for the Body Harness, Instrument Panel (IP) Harness, and the Headlamp & Dash Harness. The JB also contains the fuses and relays used for the interior electrical system of the vehicle. The combination of the BCM and the JB is called the Junction Block Module (JBM).

There are two versions of JBM's: highline and lowline. The lowline is a subset of the components in the highline. Basically the lowline JBM will not support the following: Front or Rear Fogs, Remote Keyless Entry (RKE), and Vehicle Theft Alarm (VTA). In order to reduce service inventory, only the highline will be stocked. If there is a need to replace a lowline module in the field, a highline module may be used to replace it without any noticeable difference to the customer. The relay content of the JB varies based on vehicle options (power vs. manual seats, with or without Front Fogs, etc.). On right hand drive vehicles there is a separate ground wire connected to the BCM to identify it as a right hand drive.

The BCM controls the following subsystems:
- Compass/Mini-Trip Computer
- Door Ajar System
- Exterior Lighting
- Interior Lighting
- Power Door Locks/Remote Keyless Entry
- Rear Window Defogger
- Vehicle Theft Security System
- Windshield Wipers System

The BCM also is involved in the following functions:
- Vehicle Speed Sensing (Program Tire Size)
- Detection/Analysis of Miscellaneous Body Switches
- Driver Information Warnings (Chime)

The BCM is powered via the Ignition Off Draw (IOD) fuse. This allows the BCM to be active whenever the vehicle battery is connected whether the ignition is on or not. This is necessary because the BCM controls functions which are active when the ignition is not on (power locks, VTSS, etc.). If the IOD fuse is removed (i.e. for shipping or storage), the BCM will not be powered when the ignition is off, so any ignition-off functions will not be available. To optimize battery life in a stationary vehicle with the IOD fuse in place, the BCM goes to a low power mode ("sleeps"), when it detects that there is no relevant input or output active when the ignition is off. This transition from full power mode to low power mode, and vice versa, is extremely quick and is transparent to the vehicle owner.