GM Service Manual Online
For 1990-2009 cars only

The body control module (BCM) controls the audible warnings. Refer to Body Control System Operation in Body Control System for more information.

Audible Warnings Description

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

    • Key in ignition reminder: An audible warning intended to remind the driver that the key has been left in the ignition cylinder. The BCM sounds the chime for this reminder at a rate of 150 chimes per minute.
    • Fasten seat belt reminder: An audible warning intended to remind the driver at the beginning of the driving cycle that the driver's seat belt is unfastened. The BCM sounds the chime for this reminder at a rate of 50 chimes per minute.
    • Fasten belts indicator control: A visual warning intended to remind the driver that the driver's seat belt is unfastened.
    • Parking brake reminder: An audible warning intended to remind the driver that the parking brake has been left applied with the transaxle shifted out of PARK. The BCM sounds the chime for his reminder at a rate of 200 chimes per minute.
    • Turn signal reminder:
        An audible warning intended to remind the driver that the turn signal has been left on while the vehicle has traveled over 1.2 km (0.75 mile). The BCM sounds the chime for this reminder at a variable rate (in unison with the turn lamps on) of 90 chimes per minute.
    •  Headlamps ON reminder: An audible warning intended to remind the driver that the headlamps have been left on. The BCM sounds the chime for this reminder at a rate of 200 chimes per minute.
    •  Last door closed locking confirmation: An audible warning intended to provide the driver feedback that the last door closed locking feature is active. The BCM sounds the chime for this remainder at a rate of 200 chimes per minute.
    •  Feature customization and diagnostics feedback: An audible feedback used when changing feature customization modes. This is also used by service technicians during the BCM diagnostics. The BCM sounds the chime during the feature customization, and also during diagnostics. Refer to Diagnostic Starting Point in Body Control System for additional information.

Key In Ignition Reminder

The BCM sounds key in ignition reminder when the following conditions are met:

    • The driver's door is open (ground signal in circuit 49).
    • The key is fully inserted in the ignition cylinder (ground signal in circuit 80).
    • The ignition switch is in the off position or the accessory position.

Fasten Seat Belt Reminder

The BCM sounds the fasten seat belt reminder ON for 6 (+/-2) seconds when the following conditions are met:

    • The ignition switch is turned from the off position to the on position, or from the start position to the on position.
    • The driver's seat belt is unfastened (ground signal in circuit 238).

If the driver's seat belt is fastened, then unfastened within 6 seconds chime period, the BCM stops the chime while the driver's seat belt is fastened. The BCM resumes the chime for reminder of 6 second period if the driver's seat belt is unfastened.

Fasten Belt Indicator Control

The BCM sends a request to the instrument cluster via Class 2 serial data link to turn on the fasten belts indicator for 75 (+/- 7.5) seconds when the following conditions are met:

    • The ignition switch is on.
    • The driver's seat belt is unfastened (ground signal in circuit 238).

If the driver's seat belt is fastened during the 75 second period, the BCM sends a request to the instrument cluster via Class 2 serial data link to turn off the fasten belts indicator. The BCM sends a request to the instrument cluster to turn on the fasten belts indicator for 75 (+/- 7.5) seconds (repeating this sequence) if the driver's seat belt is unfastened during the same ignition cycle. The instrument cluster turns on steadily the fasten belts indicator lamp during the first 20 seconds, then the fasten belts indicator flashes.

Parking Brake Reminder

The BCM sounds the parking brake reminder when the following conditions are met:

    • The ignition switch is on.
    • The parking brake switch is closed, sending a ground signal in circuit 1830. This indicates that the parking brake is set (applied).
    • The transaxle is shifted out of PARK or NEUTRAL by sensing a transaxle range PRNDL signal via the Class 2 serial data link

Turn Signal Reminder

The BCM sounds the turn signal reminder once per each flash of the turn signal lights when the following conditions are met:

    • The ignition switch is on.
    • The turn signal switch is in either the left turn position or the right turn position (sensing, in the past 2 seconds, a turn signal on signal via the Class 2 serial data link.)
    • The vehicle has traveled a distance of 1.2 km (0.75 mile) by sensing vehicle speed signals via the Class 2 serial data link.

The BCM keeps active the turn signal reminder until one of the following conditions is met:

    • The ignition switch is off.
    • The turn signal switch returns to the off position (sensing, in the past 2 seconds, no turn signal signals via the Class 2 serial data link.)

Headlamps On Reminder

The BCM sounds the headlamps on reminder when the following conditions are met:

    • The driver's door is open (ground signal in circuit 49).
    • The headlamp switch is in either PARK or HEAD position (open in circuit 1872).
    • The ignition switch is in the off position or the accessory position.

Key in Ignition Switch Input

The BCM interfaces with the ignition key alarm switch. The ignition key alarm switch grounds circuit 80 when the key is fully inserted in the ignition switch. The switch opens when the key is removed from the ignition switch. The BCM uses this input for the operation of the key-in-ignition reminder, lockout prevention, exit lighting, among other BCM-related features. The ignition key alarm switch receives ground through circuit 1550.

Driver's Door Ajar Switch Input

The BCM uses this input for the operation of the key-in-ignition reminder and headlamps on reminder. When the driver's door is open, the door lock switch grounds circuit 49. Refer to Interior Lights Circuit Description in Lighting Systems for more information regarding the driver's door lock ajar switch input.

Driver Seat Belt Switch Input

The BCM determines when the driver's seat belt is fastened through the seat belt switch. The seat belt switch opens when the driver's seat belt is fastened. When the driver's seat belt is unfastened, the seat belt switch closes. This causes the switch to ground circuit 238. The BCM uses this input for the operation of the fasten belts indicator lamp and chime reminder.

Park Brake Input

The BCM determines when the parking brake is applied through the park brake indicator switch. When the parking brake is released, the park brake indicator switch opens. The park brake indicator switch closes when the parking brake is applied. This causes the switch to ground circuit 1830. The BCM uses this input for the operation of the parking brake reminder.

Park Lamp Off Input

The BCM senses a voltage signal through the park lights off input (circuit 1872) when the headlamp switch is in the PARK position or the HEAD position. The BCM uses this input for the operation of the headlamps on reminder.

Class 2 Serial Data Link

The BCM determines when the turn signal switch is on, and the vehicle traveled distance via the Class 2 serial data link. The BCM uses this information in order to activate the turn signal reminder.

The BCM determines when the transaxle is shifted out of PARK via the Class 2 serial data link. The BCM uses this information in order to activate the park brake reminder.

The instrument cluster uses the Class 2 serial data link when requesting the BCM to sound the low fuel reminder.

The BCM uses the Class 2 serial data link when requesting the instrument cluster to turn on the Fasten Belts indicator lamp.

Refer to Body Control System Circuit Description in Body Control System for more information.