The body control module (BCM) controls the following systems:

A/C Compressor Control

The Powertrain Control Module (PCM) and the BCM share the hardware and the software for control of the A/C compressor clutch. The PCM and the BCM communicate this information over the Class 2 serial data line. The BCM receives an A/C request signal from the heater A/C control assembly and transmits this signal to the PCM in order to engage the A/C clutch.

Audible Warnings

The BCM determines the priority of the chime requests and the highest priority chime request is activated. The functions which cause the audible warning to be activated by the BCM are listed from lowest to highest priority:

1. Automatic door lock-delayed locking verification
2. Automatic door lock-programming option notification
3. Check gauges
4. Headlights left on
5. Key left in the ignition
6. Oil life reset
7. Park brake on
8. Tire Inflation Monitoring System (TIMS) reset
9. Turn signal left on
10. Seatbelt not fastened

Only 1 alarm may be on at a given time. For simultaneous chime conditions, the chimes have the priority level as listed. For simultaneous chime conditions, the BCM completes all of the pending low priority alarms after completing the higher priority alarms.

Check Gauges

The check-gauges alarm sounds 3 tones, at a rate of 50 tones per minute, once per ignition cycle (once per each indicator transition to active) when any of the following indicators become active, the engine is running, and more than 5 seconds have elapsed since the engine began running:

Headlamp On Warning System Description and Overview

The headlamps ON alarm sounds at a rate of 300 tones per minute when the following conditions are true:

The alarm deactivates when any one of the above conditions changes.

Key In Ignition

The key-in-ignition alarm sounds at a rate of 150 tones per minute for 3  seconds , then switch to 18 tones per minute when the following conditions are true:

The alarm deactivates when any one of the above conditions changes.

Oil Life Reset

The oil life reset acknowledgment alarm sounds 5 tones, at a rate of 50 tones per minute when the cluster transmits an Engine Oil Fluid Remaining Life Command=100% to the PCM.

Park Brake Warning

The Park Brake alarm sounds at a rate of 300 tones per minute when the following conditions are true:

The alarm deactivates when any one of the above conditions changes.

Seatbelt Not Fastened

The seatbelt-not-fastened alarm sounds at a rate of 50 tones per minute when the following conditions are true:

The alarm deactivates when any one of the above conditions changes.

Tire Inflation Reset

The tire inflation reset acknowledgment alarm sounds 5 tones, at a rate of 50 tones per minute when the low tire pressure reset report is sent out by the EBCM.

Turn Signal (Oldsmobile only)

The turn signal--on alarm activates when ignition is active and the turn signal has been active for greater than 1.2 km (0.75 mi). The alarm synchronizes with the turn signal flash rate.

Battery Rundown Protection

Battery Rundown Protection helps prevent the battery from deep discharge when you have inadvertently left the interior/courtesy lighting on (glove box door open, door ajar, map light on, etc.). Battery Rundown Protection performs this function by turning off the inadvertent power output. This provides a battery voltage for the interior/courtesy lighting.

Once the ignition switch is turned off, a time-out period begins. When the time-out expires, the inadvertent output is turned off. The length of time before the timer expires depends on the accumulative vehicle mileage. If the mileage is under 24 km (15 mi), the vehicle is assumed to be in the plant or the dealership lot, and the time out period of 3 minutes is used. If the accumulative mileage is greater than 24 km (15 mi), the vehicle is assumed to be in the hands of the customer, and time out period of 20 minutes is used.

While the inadvertent power output is off, the inadvertent feed back is monitored. If a high to low transition occurs, or if a hardware/software wake up occurs, the inadvertent output is turned back on and the timer is restarted.

Cruise Cancel (Oldsmobile only)

The Cruise Cancel Switch operates in the following manner. The BCM reads the cruise control cancel switch and determines when the switch is pressed. The BCM transmits a Class 2 serial data message to the PCM to disable the cruise.

Driver Warning System

The BCM is responsible for interpreting most of the driver warnings. The remaining driver warning information is sent on to the instrument cluster in the form of a Class 2 serial data bus message. The BCM sends the following messages to the instrument cluster :

ABS Indicator

The amber ABS indicator illuminates when the EBCM transmits a Class 2 serial data message to the instrument cluster indicating an ABS malfunction. The instrument cluster commands the ABS indicator on. In the event of a Class 2 serial data loss, the ABS indicator illuminates.

Brake Indicator

The red BRAKE indicator illuminates when the ignition switch is active and the park brake is engaged. The BCM transmits a Class 2 serial data message to the instrument cluster indicating the park brake status. Also, the BRAKE indicator illuminates when the EBCM detects a brake fail condition. The instrument cluster commands the BRAKE indicator on. The BRAKE Indicator turns off under the following conditions:

If the EBCM commands the BRAKE indicator to illuminate, the cruise function is canceled. In the event of an EBCM Class 2 serial data loss, the BRAKE indicator illuminates . In the event of a BCM Class 2 serial data loss, the park brake status and the indicator remain in their last states.

Check Tire Pressure (Pontiac) / Low Tire Pressure (Oldsmobile)

The amber CHECK TIRE PRESSURE (Pontiac) or the LOW TIRE PRESSURE (Oldsmobile) indicator is commanded on by the EBCM via a Class 2 serial data message to the instrument cluster.

To reset the tire pressure, the BCM reads a momentary switch found in the LH IP Junction Block and transmits a Class 2 serial data message to the instrument cluster. The switch must be momentarily depressed twice (2) in order to enter the Tire Inflation Monitoring System (TIMS) reset stage. At this point the CHECK TIRE PRESSURE (Pontiac) LOW TIRE PRESSURE (Oldsmobile) flashes at 1 Hz by the instrument cluster to inform the driver that the TIMS reset has chosen Oil Life or TIMS. The driver then has a time period to depress and hold the switch. Once this condition is met the instrument cluster sends out a Class 2 serial data Low Tire Pressure Reset message. The EBCM reacts to this message by determining the new tire pressure. In addition, the indicator illuminates for a period of time and then turns off when the reset period is complete. The reset program is exited under either of the following conditions:

When the BCM receives the reset acknowledge report from the EBCM, an acknowledgment chime shall sound.

Upon a loss of Class 2 serial data between the EBCM and the instrument cluster, the commanded indicator remains in its last state. Upon a loss of Class 2 serial data between the BCM and the instrument cluster, the BCM commanded chime state remains off.

Change Oil/Oil Life Indicator

The PCM performs a powertrain specified oil life program and transmits a Class 2 Oil Life serial data message to the instrument cluster indicating the percent of oil life remaining. The instrument cluster compares the percent oil life remaining to a calibrated threshold and dictates the CHANGE OIL/OIL LIFE indicator state.

To reset the Oil Life indicator, the BCM reads a momentary reset switch input and transmits a Class 2 serial data message to the instrument cluster indicating that the switch has been closed. The switch must be momentarily depressed, for 3 seconds, in order to enter the Oil Life reset stage. At this point the instrument cluster flashes the CHANGE OIL/OIL LIFE indicator at 1 Hz in order to inform the driver that this program is the one chosen to be reset. (You can also reset Oil Life or Tire Inflation Monitoring System from this switch). The driver then has 3 seconds to depress and hold the switch. The instrument cluster sends out a Class 2 Oil Life serial data command message. The PCM reacts to this message by resetting the remaining oil life to 100%. In addition, the CHANGE OIL / OIL LIFE indicator goes on solid for a period of time and then turns off when the reset period is complete. The reset program is exited if either one of the following conditions is true:

When the BCM receives the command from the instrument cluster, an acknowledgment chime shall sound.

In the event of a PCM Class 2 serial data failure, the instrument cluster commanded indicator shall remain in its last state. In the event of a BCM Class 2 serial data failure, the chime shall not be triggered.

Check Oil Indicator (V6 only)

The amber check oil indicator illuminates when the PCM reads the oil level switch and transmits a Class 2 message to instrument cluster indicating a low oil level condition. If the low oil level option is false, all Class 2 activity on the instrument cluster stops. The instrument cluster will not send out any request for the low oil level condition command and will not issue a low oil level condition report. If a loss of PCM Class 2 serial data occurs, the check oil indicator will not illuminate unless the indicator was illuminated when the event occurred.

Cruise Indicator

The green CRUISE indicator illuminates when the PCM transmits a Class 2 message to the instrument cluster indicating that cruise control is engaged. The instrument cluster commands the CRUISE indicator on. If the EBCM commands the BRAKE indicator to illuminate, the cruise function is canceled. If a Class 2 serial data loss occurs, the CRUISE indicator will not be illuminated unless the indicator was illuminated prior to the event.

High Temperature Indicator

The high temperature indicator function handles the control of the engine temperature gauge display and the red high temperature indicator. The PCM reads the coolant temperature sensor, filters the messages, and sends the coolant temperature to the instrument cluster via a Class 2 serial data message. The PCM monitors the coolant sensor in order to determine a fault. The PCM transmits the Class 2 serial data coolant temperature report messages to the instrument cluster for the temperature gauge display and for the high temperature indicator control.

The instrument cluster receives the engine temperature data in the Class 2 serial data message from the PCM. The instrument cluster converts this data into a temperature gauge pointer position which drives the gauge pointer. The instrument cluster also uses this data in order to determine the high temperature indicator control.

The BCM looks for the high temperature indicator Class 2 serial data report from the instrument cluster and triggers a chime when the indicator is on.

High Beam Indicator

The blue high beam indicator is a distributed function between the BCM and the instrument cluster. The BCM reads the high beam bulb voltage, and divides by the system voltage in order to determine a percent value. This value is compared against a calibration in order to determine if the high beams are on. The BCM then transmits the status of the high beams to the instrument cluster via the Class 2 serial data bus. The instrument cluster then commands the high beam indicator accordingly. In the event of a Class 2 data link failure, the high beam indicator will not illuminate unless the indicator was illuminated prior to the Class 2 data link failure.

Low Engine Coolant Indicator

The red low coolant indicator illuminates in order to indicate to the driver that the engine coolant level is low. The engine coolant level switch is a discrete input to the BCM which closes when the engine coolant is low. The indicator illuminates when the input has been active low for at least 10 seconds and the ignition switch is in the ON position. The indicator is commanded off if the switch input goes inactive for at least 2 seconds. This is a distributed function between the BCM and the instrument cluster. The BCM reads the status of the engine coolant level switch input in order to determine the indicator control. Then the BCM sends the control state to the instrument cluster via the Class 2 serial data bus. The instrument cluster reads the low coolant indicator control state in the Class 2 serial data message and controls the indicator directly. If a Class 2 data link fails, the low coolant indicator illuminates.

Low Fuel Indicator

The amber low fuel indicator turns on in order to indicate to the driver that the fuel level has dropped to a calibrated point below 1/16 of a tank. The indicator is turned off when the fuel level rises back above 1/16 of a tank. The fuel level is determined from the fuel level sense and display function and is then used by the low fuel indicator. This is a distributed function between the PCM and the instrument cluster. The instrument cluster reads the low fuel indicator control state in the Class 2 message and controls the indicator directly. If a Class 2 data link fails, the low fuel indicator does not illuminate unless the indicator was illuminated prior to the Class 2 data link failure.

Low Wash Indicator

The amber LOW WASH indicator turns on in order to indicate to the driver that the washer fluid level is low. The low washer fluid level switch is a discrete input to the BCM which closes when the washer fluid level is low. The BCM commands the instrument cluster to illuminate the indicator when the input has been active for a calibratable time (at least 30 seconds). The BCM commands the instrument cluster to turn the indicator off, if the switch input goes inactive for a calibratable time (at least 30 seconds). If a Class 2 data link fails, the LOW WASH indicator does not illuminate unless the indicator was illuminated prior to the Class 2 data link failure.

Oil Pressure Indicator

The red oil pressure indicator turns on when the PCM transmits a Class 2 message to the instrument cluster indicating a low oil pressure condition. The instrument cluster commands the oil pressure indicator on over the Class 2 serial data interface. If a loss of Class 2 serial data occurs, the oil pressure indicator does not illuminate unless the indicator was illuminated when the event occurred. If a Class 2 data link fails, the oil pressure indicator does not illuminate unless the indicator was illuminated prior to the Class 2 data link failure.

PRNDL

The PCM reads the transaxle range switch and transmits the selected gear position over the Class 2 serial data link to the instrument cluster.

Seat Belt Indicator

The seat belt switch is a discrete input to the BCM which opens when you insert the seat belt into the buckle. The BCM commands the instrument cluster to illuminate the red seat belt indicator under either of the following conditions:

Upon either transition, the seat belt indicator glows steady for 20 seconds and then flashes at 1 Hz for 55 seconds. The indicator turns off when any one of the following conditions becomes true:

If a Class 2 data link fails, the seat belt indicator does not illuminate unless the indicator was illuminated prior to the Class 2 data link failure.

SERVICE VEHICLE SOON Indicator

The amber SERVICE VEHICLE SOON indicator is an alert to the driver whenever there are specific current codes stored in the BCM or in the event of a loss of Class 2 serial data.

Security Indicator

The red SECURITY lamp illuminates when the Passlock® data isincorrect. The BCM sends to the instrument cluster via the Class 2 serial data bus the message to turn on or off the SECURITY indicator. The SECURITY indicator turns on under either of the following conditions:

The SECURITY indicator flashes when the BCM detects a tamper or the PCM fuel disable time-out bit is set in the last vehicle security status message received since the ignition switch was turned to the ON position.

Enhanced Traction Control-TRAC OFF Indicator

The EBCM receives a Class 2 serial data message from the BCM indicating a traction switch activation. The EBCM determines the state of the TRAC OFF indicator and sends a Class 2 serial data message to the instrument cluster commanding the indicator state. The traction control switch is a momentary switch input into the BCM which detects the switch activation and sends the Class 2 serial data message. If an EBCM Class 2 failure occurs, the TRAC OFF indicator will not illuminate unless the indicator was illuminated prior to the Class 2 failure.

Exterior Lighting Control

The BCM controls exterior lighting systems which includes the following:

Daytime Running Lights (DRL) operate the headlamps (Pontiac) or high beams only (Oldsmobile) at a reduced intensity under the following conditions:

The DRL activates if the transmission is not in PARK and the park brake is off. The DRLs remain on and latch on if the park brake is on and the vehicle speed is above the threshold. The vehicle is defined to be in motion if the transmission is not in PARK and the park brake is not set.

Automatic lighting control turns on the parklamps and the headlamps when the ambient light sensor detects a low ambient light level. The system assures that the headlamps/parklamps are on if the driver is operating the vehicle after dark.

If the ignition switch is turned to the ON position in a low ambient light level area, the automatic lighting control becomes active immediately, otherwise 8 seconds must elapse before the automatic lighting control is activated. If the park brake is set when the ignition switch is turned to the ON position, the automatic lighting control is disabled until the park brake is released. If the automatic lighting control is active and a high ambient light level is detected, 20 seconds must elapse before the automatic lighting control is turned off. The headlamps are disabled during engine crank.

The front foglamp relay activates when all of the following conditions occur:

Foglamp relays are always off whenever a short to battery fault is detected on the foglamp relay output driver.

The backup lamps are the only exterior lamps that are not controlled by the BCM.

Engine Coolant Temperature

The BCM handles the control of engine temperature gauge display and the high temperature indicator.

The PCM reads the engine coolant temperature sensor, filters the data, and sends the engine coolant temperature to the instrument cluster via a Class 2 serial data message. The PCM transmits the Class 2 serial data coolant temperature report messages to the instrument cluster in order to determine the temperature gauge display and to the high temperature indicator control.

The instrument cluster receives the engine temperature data in the Class 2 serial data message from the PCM and converts this message into a temperature gauge pointer position which drives the gauge pointer. The instrument cluster also uses this message in order to determine the high temperature indicator control.

The BCM looks for the high temperature indicator Class 2 serial data report from the instrument cluster and triggers a chime when the indicator is on.

Fuel Level Sensing

The PCM reads the fuel level sensor, filters the data, and then sends a fuel level Class 2 serial data message to the instrument cluster for display. The instrument cluster drives the fuel gauge pointer. The PCM is responsible for sending a fuel related Class 2 serial data message so that fuel level sensing is started when Ignition 0 is on, however the fuel level is not displayed until Ignition 1 is on. This is done in order to reduce the latency of the fuel gauge display during key-on.

The BCM looks for the low fuel indicator Class 2 serial data report from the instrument cluster and triggers a chime when the indicator is on.

Interior Lighting Control

The interior light control function provides convenience and security by turning on the interior courtesy lights under several conditions. The following conditions enable the courtesy lamps:

When the driver leaves the vehicle (the ignition switch is turned off for more than 2 minutes), the interior lights are first step dimmed, and then theater dimmed to the off state.

Panic Alarm

The panic alarm is an alarm system that you can trigger by pressing the panic button on the remote control door lock transmitter. This sends a Class 2 serial data message to the BCM which triggers the panic alarm. The parklamps and the horn alternately cycle on and off for up to 2 minutes. If you turn the ignition switch to the ON position or if you press the panic button while the panic alarm is active, the alarm immediately turns off. If the delayed off automatic lighting control (ALC) function is active when you trigger the panic alarm, the ALC parklamp control is overridden in order to control the cycling of the parklamps. If you request the remote control door lock receiver horn chirp while the panic alarm is triggered, the chirp request is ignored.

Rear Compartment Lid Release

The rear compartment lid release system allows you to release the rear compartment lid electrically in one of 2 different ways:

In order to operate the rear compartment lid release system, one of the following must be true:

Vehicle Theft Deterrent (VTD)

The red security indicator is a distributed function between the BCM and the instrument cluster. The BCM determines the status of the security indicator based on its internal Passlock® algorithm and what has been communicated to it from the PCM Passlock® algorithm. The BCM then forwards a status of either OFF, ON or FLASH to the instrument cluster over the Class 2 serial data bus. If the indicator status is FLASH, the instrument cluster actually controls the flash rate/timing.

The SECURITY indicator shows whether the Passlock® data has passed. The BCM sends a message to turn the SECURITY indicator on or off to the instrument panel cluster (IPC) via the Class 2 serial data bus.

The SECURITY indicator is on when the BCM is not in the auto-learn mode and either of the following conditions is true:

The SECURITY indicator flashes when either of the following conditions is true:

If the BCM is in a 10-minute tamper and the ignition switch is turned to the OFF position, the instrument cluster remains awake and flashes the SECURITY indicator until the BCM requests a status of OFF. The instrument cluster has a maximum wait time defined.

Wake-up/Asleep States

Wake-ups are signals that turn on the BCM and cause the BCM to begin active control and/or monitoring. The BCM wake-ups are as follows: