Operation

OPERATION

The microprocessor-based Body Control Module (BCM) monitors many hard wired switch and sensor inputs as well as those resources it shares with other electronic modules in the vehicle through its communication over the Programmable Communications Interface (PCI) data bus or the hybrid bus network. The internal programming and all of these inputs allow the BCM microprocessor to determine the tasks it needs to perform and their priorities, as well as both the standard and optional features that it should provide. The BCM programming then performs those tasks and provides those features through both PCI data bus or hybrid bus communication with other electronic modules and through hard wired outputs through a number of driver circuits, relays, and actuators. These outputs allow the BCM the ability to control numerous accessory systems in the vehicle.

The BCM operates on battery and ignition voltage inputs received through several fuses in the Junction Block (JB) on a non-switched fused B(+) circuit, through another fuse in the JB on a fused ignition switch output (run-start) circuit, and through a third fuse in the JB on a fused ignition switch output (run-acc) circuit. This arrangement allows the BCM to provide some features regardless of the ignition switch position, while other features will operate only with the ignition switch in the ON, START, or ACCESSORY positions. All of the battery voltage circuits are connected to the BCM through the JB/BCM connector.

The BCM receives ground through five separate circuits. Three of these circuits are connected to the BCM through a connector of the instrument panel wire harness on three separate ground circuits, while the other two circuits are connected to the BCM through the JB/BCM connector. Each of these circuits receives a path to ground through the instrument panel wire harness with an eyelet terminal connector that is secured by a nut to a ground stud on the driver side instrument panel end bracket near the JB.

The BCM monitors its own internal circuitry as well as many of its input and output circuits, and will store a Diagnostic Trouble Code (DTC) in electronic memory for any failure it detects. These DTCs can be retrieved and diagnosed using a diagnostic scan tool. Refer to the appropriate diagnostic information.

INPUT AND OUTPUT CIRCUITS

HARD WIRED INPUTS

The hard wired inputs to the BCM include the following:

- A/C on/off control
- BCM flash enable
- Door lock switch mux
- Driver door ajar switch sense
- Flip-up glass ajar switch sense
- Flip-up glass release switch sense
- Front fog lamp switch sense
- Front wiper park switch sense
- Front wiper switch mux
- Fused B(+)
- Fused ignition switch output (run-acc)
- Fused ignition switch output (run-start)
- Headlamp switch mux
- High beam switch sense
- Hood ajar switch sense - with VTSS - in markets where required only
- Key-in ignition switch sense
- Left rear door ajar switch sense
- Lightbar switch sense - Renegade with light bar only
- Panel lamps dimmer switch mux
- Passenger front door ajar switch sense
- Radio control mux - with remote radio switches only
- Rear courtesy lamp control
- Rear window defogger control
- Rear wiper intermittent driver
- Rear wiper on driver
- RHD input - connected to ground on right-hand drive vehicles only
- Right rear door ajar switch sense
- Tailgate ajar switch sense
- Washer pump driver
- Vehicle speed signal

Refer to the appropriate wiring information for additional details.

HARD WIRED OUTPUTS

The hard wired outputs of the BCM include the following:

- Accessory delay relay control - power sunroof only
- Courtesy lamp driver
- Courtesy lamp load shed
- Door lock relay control
- Door unlock relay control
- Driver door unlock relay control
- Flip-up glass release motor driver
- Front fog lamp relay control
- Front wiper high/low relay control
- Front wiper on/off relay control
- Fused B(+) - lock, unlock and driver unlock relay feed
- Hazard lamp control
- High beam relay control
- Horn relay control
- Instrument cluster wake up signal
- Low beam relay control
- Park lamp relay control
- Rear fog lamp relay control - with rear fog lamps in markets where required only
- Rear window defogger relay control
- Tailgate lock driver
- Tailgate unlock driver
- Vehicle speed output
- Vehicle speed sensor supply - except with Antilock Brake System (ABS)
- VTSS indicator driver - with VTSS only

Refer to the appropriate wiring information for additional details.

GROUNDS

The BCM receives ground through five separate circuits, and also supplies a clean ground path to several switches through the following hard wired circuits:

- Door lock switch ground
- Multi-function switch ground
- Radio control mux return
- Tailgate switch ground

Refer to the appropriate wiring information for additional details.

COMMUNICATION

The BCM has the following communication circuits:

- PCI bus
- CAN-C High bus - with ESP only
- CAN-C Low bus - with ESP only

Refer to the appropriate wiring information for additional details.