Module, Body Control: Operation: Operation: Notes

The Body Control Module (BCM) supplies vehicle occupants with visual and audible information and controls various vehicle functions. To provide and receive information, the BCM is interfaced to the vehicle's serial bus communications network, referred to as the Programmable Communications Interface (PCI) data bus.

This network consists of the: 

• Audio system equipped with RBQ radio.
• Controller Antilock Brake (CAB)
• Electro Mechanical Instrument Cluster (EMIC)
• HVAC Control Module
• Occupant Restraint Controller (ORC)
• Powertrain Control Module (PCM)

The BCM is operational when battery power is supplied to the module and after the ignition is FIRST powered to RUN or the driver side exterior door handle is pressed.

The BCM provides the following features: 

• Adjustable Pedal - Operates adjustable pedals (non memory applications). BCM supplies the high side driver directly to switch that feeds the adjustable pedals
• Ambient Temperature Sensor - Based on configuration: The BCM reads the temp sensor or the DDCM reads sensor and sends Bus message to BCM. The BCM sends a bus message to IC and TGW
• Automatic Door Locks
• Battery Protection - The BCM will automatically turn off all exterior lamps after 3 minutes, and all interior lamps after 15 minutes after the ignition is turned off, if they are not turned off by the driver.
• Battery Save Mode
• BCM Diagnostic Reporting
• Brake Fluid Level - Brake fluid level bus message to IC. This is a hardwired input to BCM.
• Brake Transmission Shift Interlock (BTSI) - Provides power to BTSI.
• Bus Gateway - Passes messages between CAN I, CAN C and LIN buses. Communicates with scan tool over CAN C.
• Chime Control
• Deck lid Release (RKE only)
• Door Ajar - Monitors door, liftgate, Flipper glass and Trunk Ajar. Hardwired input to BCM from all door, trunk and liftgate ajar switches. BCM sends message to IC, PCM
• Door Lock Inhibit - This feature disables the door lock functions if the key is in the ignition and either front door is ajar. Pressing the Remote Keyless Entry (RKE) lock/unlock button under these conditions result in normal lock/unlock activation.
• ESM (feed) - Provides power to transmission shift module. High side drive from BCM when Run/Start.
• Exterior Lighting -
  • Operates Headlights, High beam, Low beam, AUX, Turn signals, Fog lamps, Park lamps, Side marker, Stop/Tail lamps, Cargo lamp, CHMSL, baggage/trunk lamps and license plate lamps. BCM directly reads headlamp switch and controls lamps.
  • Operates Auto Headlamps. BCM receives a bus message from HVAC or RSLM. Based on configuration: if configured for Tunnel detect present then uses RSLM sensor and TDM, If configured for Twilight sensor uses twilight sensor and HVAC sends message.
  • Operates High beam and Turn signal. SCCM reads switch and sends bus message to BCM.
  • Operates Hazard lamps. BCM directly reads digital hazard switch to ground.
  • Operates Reverse lamps. Hardwired switch for Manual Trans or bussed message from TCM.
  • Operates Right, Left brake lamps and CHMSL. 12 volt signal from Brake switch or ABS/ESP to BCM.
  • Dedicated DRL. BCM operates based on IGN RUN, Engine status RPM, and transmission position Drive.
• Fade to Off Interior Lamps - This feature dims the interior lighting (courtesy lamps) gradually if the BCM does not receive any new inputs that would cause the interior lamps to remain on.
• Fuel Door - Operates Fuel door relay. BCM reads Fuel door release switch.
• Fuel Level - BCM reads the fuel level sensor and busses this information to the IC.
• Headlamp Time Delay
• Hood Ajar Status #1 - Hood ajar switch status for remote start, or some security systems. This is a hardwired switch input to BCM. Status used by BCM, and bus message sent to IC
• Hood Ajar Status #2 - Hardwired switch input to BCM.
• Horn
• Ignition Interface - Operate IGN RUN external relays in PDC - Bussed message and redundant hardwired run/start input from RFHUB.
• Interior Lighting (Courtesy/Reading Lamps)
  • Operates Most Courtesy lamps. Some powered by DDM.
  • Operates Convenience lamps - Map lights, HALO, Foot well and Glove box lamp.
  • Ambient Light dimming Wheel - Reads level and adjust lights, sends level on CAN bus to other modules.
• Parking Brake - BCM reads switch (Active Low). BCM busses message to the IC.
• Power accessory delay - Provides power to various modules like radio and windows. BCM holds RUN Accy #1 and #2 relays ON. Delay time is configurable.
• Power Door Locks - Operates lock/unlock relays. Bus message from door nodes, RFHUB or hardwired from door switches.
  NOTE:

  Power Door Lock Note - 

  The BCM implements a software PTC (positive thermal coefficient) algorithm to protect the door lock motors. The BCM will allow approximately 21 actuations before it regulates them according to elapsed time between actuations. BCM will shut off the door lock motors after 21 actuations for cool down. After shutdown you will get 1 activation back every 7 seconds there are no door lock/unlock requests.

  Power Windows - Includes Auto Down feature

• Remote Keyless Entry (RKE)
• Security system - Operates Horn, exterior lamps and VTA LED. BCM is security master.
• Smart Glass
• Tip start and Remote Start - Operates the starter solenoid - Bussed messages and Hardwired inputs from RFHUB & PCM, PCM controls low side of relay coil (double start override). The BCM controls the high side of relay coil.
• Tire Pressure Fault Detection
• Trunk Release - Operates trunk release. BCM reads Trunk release switch (Active Low).
• UGDO - Provides power to UGDO. BCM provides power to the UGDO module when awake.
• Washers and Wipers -
  • Operates windshield washer motor. SCCM reads switch and sends bus message to BCM.
  • Operates Front wipers. SCCM reads switch and sends bus message to BCM.
  • Parks wipers - Front. Hardwired input to the BCM.
  • Washer fluid level. Hardwired input sensor to the BCM.
• Vehicle Theft Security
• Virtual Lock Automatic Door Locks

All features on the BCM are standard except Daytime Running Lamps (DRL). The customer/dealer has the ability enable or disable the following features: 

• Auto Lock Disable
• Daytime Running Lamps Enable (U.S. - Option, Canada - Enabled)
• Headlamp Delay Disable
• Power Accessory Delay Disable
• RKE Horn Chirp Disable
• RKE Optical chirp Disable
• RKE Unlock - All - one press Enable

Systems the BCM does not operate (other than in its role as the Gateway or IGN RUN power feeds): 

• Fuel Heater (IGN RUN Relay feed)
• A/C Clutch
• Wheel Speed
• A/C pressure
• Radiator Fan Control
• HVAC (HVAC Control Module)
• Keyless Entry (RFHUB)
• Battery Charging (PCM or Alternator)
• Power Windows (high current switch or door node, Accy power is shut off by BCM if doors are open during accy. Delay mode).
• Engine Control (other than providing power and ignition states to PCM).
• Mirror Turn Signal (door control module provides power based on bus message).

POWER FEEDS: 

• BAT1= Exterior lighting 1 40A fuse in PDC
• BAT2= Exterior lighting 2 40A fuse in PDC
• BAT3= Interior lighting 30A fuse in PDC
• BAT4= Door locks 30A fuse in PDC

WAKE UP INPUTS: 

Inputs that will wake up the CAN BUS when activated are:

• IGN RUN-START
• ESP BRAKE SIGNAL
• Headlamp Switch
• Dimmer Wheel
• Hazard Switch
• Convenience lamp switch
• Sunshade Switch
• Door Ajar
• Trunk Ajar
• Door lock switches
• Trunk release
• Hood ajar
• CAN signal

OUTPUTS LOCKED OFF:  BCM output driver circuits have a retry strategy. If the output has executed all of it's possible retries before a fault (short to GND or Battery) is removed, the fault will remain active until the next ignition cycle. There are only 4 retries in one ignition cycle. A fault on the last retry will lock off the output and will not turn it on again until an ignition cycle off/on.

The BCM has internal diagnostic capability that assists in diagnosing the system error. When an OPEN or a SHORT circuit exists, the diagnostic tool can be used to read the BCM faults. The faults are very descriptive in identifying the appropriate feature that has faulted.

The only two faults that the BCM logs that conclude the replacement of a BCM are faults;

• # 06 - Internal BCM failure (replace BCM)
• # 31 - J1850 Internal Hardware Failure (replace BCM)

Otherwise the appropriate diagnostic procedures for each of the features should be taken when the BCM logs a fault. Refer to DIAGNOSIS AND TESTING .