GM Service Manual Online
For 1990-2009 cars only

Remote Function Actuator (RFA)

The RFA module is part of the remote keyless entry system. The RFA module sends a serial data message to the body control module (BCM) through a dedicated serial data line. The RFA module is not on the Class 2 serial data network. The following commands are sent to the RFA module by the RFA transmitter (Key Fob):

    • The door lock and unlock control
    • The lift glass release
    • The panic alarm

The RFA module then sends a serial data message to the BCM in order to perform the appropriate function. Refer to Transmitter Programming for programming of the RFA system.

Wake-Up State

The following wake-up signals will turn ON the BCM. The BCM can then begin active control and/or monitoring of certain devices:

    • The door ajar switches
    • The door handle switches (utility only)
    • The dome lamp
    • The park lamps
    • The power door lock switches
    • The gate ajar switch
    • The interior lamp request active
    • The ignition key put into the ignition switch
    • The ignition key removed from the ignition switch
    • The ignition in the RUN position
    • The key in the door lock switch (Envoy only)
    • The lift glass release switch
    • The lift glass jamb switch
    • The RFA request to the BCM
    • Any Class 2 communication that requires BCM interaction

Asleep States

The BCM is asleep when the BCM has stopped controlling or monitoring devices and has become idle again.

The BCM enters the asleep state and goes into the low power mode when the following conditions exist:

    • The ignition switch is in the LOCK position.
    • 20 minutes elapse without any wake-up signals.

If the BCM is in the low power mode and detects a wake-up, the BCM will enter into the wake-up state and then enter the high power mode.

The BCM will return to the low power mode when the following actions occur:

    • The ignition switch is in the LOCK position.
    • 20 minutes elapse without any wake-up signals.

Ambient Level Sensor

The ambient light level sensor has the following 2 states:

    • The LIGHT state
    • The DARK state

If the headlamp switch is set to AUTO while in the LIGHT state, the following components will stay fully bright:

    • The radio
    • The PRNDL
    • The 4-wheel drive switch
    • The overhead console
    • The radio
    • The PRNDL
    • The 4-wheel drive switch
    • The overhead console
    • The radio
    • The PRNDL
    • The 4-wheel drive switch
    • The overhead console

The above components will STEP dim with the dimming control when the headlamp switch is set to one of the following positions while in the LIGHT state:

    • PARK LAMP
    • HEADLAMP

The above components will STEP dim with the dimming control when the headlamp switch is set to one of the following positions while in the DARK state:

    • AUTO
    • PARK LAMP
    • HEADLAMP

Daytime Running Lamps (DRL) and Auto Headlamps

LIGHT State

The daytime running lamps (DRL) turn ON when the following conditions exist:

    • The headlamp switch is set to the AUTO position.
    • The sensor is in the LIGHT state.

If you set the park brake, the DRLs will turn OFF. When you release the park brake, the DRLs will turn ON.

The following actions occur if the DRL is set to the PARK LAMP position:

    • The DRLs turn ON.
    • The park lamps turn ON.

The following actions occur if the headlamp switch is set to the HEADLAMP position:

    • The DRLs are OFF.
    • The park lamps are ON.
    • The headlamps are ON.

The following actions occur if the headlamp switch is set to the HEADLAMP position and the HIGH/LOW beam switch is toggled:

    • The DRLs are OFF.
    • The park lamps are ON.
    • The headlamps are ON.
    • The HIGH/LOW beams will toggle with the HIGH/LOW switch.

If the headlamp switch is set to the AUTO position and the and the ambient light level conditions change to DARK for 15 seconds, the BCM will turn ON the headlamps.

DARK State

The following actions occur is the headlamp switch is set to the AUTO, PARK LAMP or HEADLAMP position:

    • The DRLs are OFF.
    • The park lamps are ON.
    • The headlamps are ON.
    • If you toggle the HIGH/LOW beam switch, the HIGH/LOW beams will toggle.

The following conditions exist if the ignition switch is in the OFF position and the park brake is set:

    • The DRLs are OFF.
    • The park lamps are OFF.
    • The headlamps are OFF.

If you turn the ignition switch to the RUN position, the auto headlamps are defeated. If you release the park brake, the auto headlamps will function. If you set the park brake again, the headlamp function will not change.

If the headlamp switch is in the AUTO position and the ambient light level conditions change to LIGHT for 20 seconds, the BCM will turn OFF the headlamps.

Front Fog Lamps

The front fog lamps are a controlled option of the BCM. The BCM will command the fog lamp relay ON if the following actions occur:

    • The park lamps are ON.
    • The high beams are OFF.
    • You press the fog lamp switch.

The front fog lamp relay will turn the front fog lamps ON. The front fog lamp switch is a momentary switch. Only one transition occurs each time the front fog lamp switch is pressed. Press the front fog lamp switch in order to turn ON the front fog lamps. Toggle the HIGH/LOW beam switch in order to toggle the front fog lamps ON/OFF.

Remote Panic Alarm

The headlamps and the horn will activate if your press the HORN button on the RFA transmitter. Press the HORN button again in order to deactivate the headlamps and the horn.

If you press the HORN button one time, the headlamps and the horn will activate for 30 seconds or until the ignition switch is turned to the RUN position.

Passlock System

The Passlock theft deterrent system is designed to prevent vehicle operation if an incorrect ignition key is used to start the vehicle. The ignition key will allow the lock cylinder to turn. The Passlock sensor, which is located inside of the ignition switch assembly, sends a code to the BCM. If the BCM receives the correct code from the Passlock sensor, the BCM will send a password to the vehicle control module (VCM) or the powertrain control module (PCM). The message will allow the vehicle to start. Refer to Diagnostic System Check - Theft Deterrent for more Passlock system information.

Battery Rundown Protection

The battery run down protection provides protection against the following conditions:

    • Parasitic loads
    • Excessive battery drain
    • High current loads that are related to the courtesy lamp circuit

The battery run down protection will also protect the battery against being run down from the courtesy lamp circuit to a level that will prevent the vehicle from starting. The BCM will turn OFF the courtesy lamp circuit when the following actions occur:

    • The ignition switch is turned from the RUN position to the OFF position.
    • 20 minutes elapses without a lamp request input.

Complete one of the following actions in order to return the BCM to normal operation when the battery run down protection turns OFF the interior lamps:

    • Turn OFF all of the lamps and close all of the doors.
    • Turn the ignition switch from the OFF position to the ON position.

Inadvertent Power Relay

The BCM turns OFF the inadvertent power relay after 20 minutes in order to preserve the battery power. The 20 minute timer starts after any one of the following actions occurs:

    • The ignition switch is turned from RUN or START to UNLOCK, LOCK or ACC.
    • The illuminated entry is activated.
    • The interior lamps switch is turned ON.
    • The lift glass is opened or closed.
    • The underhood lamp is activated.
    • The vanity lamp is activated.
    • The courtesy lamp is activated.
    • The dome lamp is activated.
    • The glove compartment lamp is activated.
    • The reading lamp is activated.
    • The inside rear view mirror lamp is activated.

If any one of the following inputs reoccur during the 20 minute timer period, the timer is reset to 20 minutes:

    • The ignition switch is turned from RUN or START to UNLOCK, LOCK or ACC.
    • The illuminated entry is activated.
    • The interior lamps switch is turned ON.
    • The lift glass is opened or closed.
    • The courtesy lamp is activated.
    • The dome lamp is activated.

Retained Accessory Power (RAP)

The RAP feature allows the following components to be operated after the ignition switch is turned from the RUN position to the LOCK position:

    • The power windows
    • The sunroof
    • The overhead console
    • The entertainment system

The RAP operates if the vehicle battery voltage is above the minimum voltage threshold when the ignition switch is in the OFF position.

The above components will be turned off when either of the following actions occurs:

    • A door is opened.
    • 20 minutes elapses without an ignition switch transition.

Refer to Retained Accessory Power System.

Illuminated Entry

The interior lights will illuminate for 15 seconds if any of the following actions occurs:

    • For utility only, lift and release the driver door handle.
    • For utility only, lift and release the passenger side door handle.
    • Open and close the driver side door.
    • Open and close the passenger side door.

Interior Illumination

The interior lights will illuminate continuously if the following occurs:

    • The interior light defeat button is OFF and any door or the lift glass is opened.
    • The dimmer switch is rotated to the ON position for interior illumination.

Exit Lighting

The interior lights will illuminate for 40 seconds when the ignition key is removed from the ignition cylinder.

Remote Illuminated Entry

The interior lights will illuminate for 40 seconds when one of the following buttons is pressed on the RFA transmitter:

    • UNLOCK
    • LIFT GLASS RELEASE

The interior lights will illuminate for 2 seconds when the LOCK button is pressed on the RFA transmitter.

Power Door Lock/Unlock Function

The BCM is responsible for energizing the driver door unlock relay. The driver door unlock relay is energized whenever the BCM receives a command from any of the DOOR LOCK/UNLOCK switches and an input from the RFA module on the RFA serial data line.

Door Lock/Unlock Switch Function

The driver door LOCK/UNLOCK switch and the passenger door LOCK/UNLOCK switch are inputs to the BCM. The BCM will command the driver door unlock relay to unlock the drivers door according to the state of the relevant switch.

Lift Glass Release Function

The lift glass release switch is an input to the BCM. The BCM will command the lift glass to release if one of the following conditions exists:

    • The vehicle is in PARK/NEUTRAL.
    • The park brake conditions are met.
    • The lift glass release switch is pressed.

When the BCM receives a message to activate the lift glass release solenoid from the RFA module, the BCM energizes the lift glass release relay if one of the following conditions exists:

    • The vehicle is in PARK/NEUTRAL.
    • The park brake conditions are met.

Lockout Prevention

The lockout prevention feature is activated when the following actions occurs:

    • The key is in the ignition switch.
    • Any door is opened.
    • The POWER LOCK switch is pressed.

This feature will lock the doors and unlock the driver door.

Remote Lock

Press the RFA transmitter LOCK button once in order to lock all of the doors. If you press the RFA transmitter LOCK button twice within 3 seconds, all of the doors will LOCK and the horn will CHIRP.

Remote Unlock

Press the RFA transmitter UNLOCK button once and the following actions will occur:

    • The driver door will UNLOCK.
    • The park lamps will FLASH.
    • The interior lights will turn ON.

Press the RFA transmitter UNLOCK button twice within 3 seconds and the following actions will occur:

    • All the remaining doors will UNLOCK.
    • The park lamps will FLASH.
    • The interior lights will turn ON.

Press the REAR button twice within 3 seconds and the following actions will occur:

    • The lift glass will UNLOCK.
    • The park lamps will FLASH.
    • The interior lights will turn ON.

Audible Warnings

The BCM will sound a chime after the BCM determines that a driver warning sound is needed.

Key in Reminder

A chime will sound when the following conditions exist:

    • The ignition switch is not in the RUN or CRANK position.
    • The ignition key is in the ignition key cylinder.
    • The driver door is opened.

Refer to Audible Warnings for more information.

Headlamp Reminder

A chime will sound when the following conditions exist:

    • The headlamp switch is in the PARK LAMP or HEADLAMP position.
    • The dome lamp switch (thumbwheel) is not at the FULL DOWN (Max Dim) position.
    • The ignition switch is in the OFF position or ACC position.

The headlamp reminder chime will not sound if the following conditions exist:

    • The dome lamp switch is in the FULL DOWN position (Max Dim).
    • The headlamps are turned ON manually.
    • The ignition key is removed.

Refer to Audible Warnings for more information.

Seat Belt Reminder

A chime will sound for 6 seconds when the following actions occur:

    • The ignition switch is turned from the OFF position to the RUN position.
    • The seat belt is unfastened.

The seat belt telltale on the instrument panel cluster (IPC) will also turn ON. Refer to Audible Warnings for more information.

Turn Signal Reminder

A chime will sound when the right or left turn signal is turned ON for more than 0.75 miles. The chime will be synchronous with the turn signal flasher. Refer to Audible Warnings for more information.

Driver Warning Telltales

The BCM sends requests to the IP cluster in order to turn the IPC telltales ON or OFF. These requests are sent on the Class 2 serial data line. If the IPC cannot communicate with the BCM via Class 2, the IPC will turn the security telltale ON steady. The following messages are sent by the BCM to the IPC:

    • Gate ajar (utility only)
    • Over speed (export only)
    • Park brake
    • Seat belt
    • Security light
    • Turn signal reminder
    • High beam ON indicator

Lighting Control

Exterior Lighting Control

The BCM can turn ON some of the exterior lighting independently of the exterior lighting system. The vehicle lighting system controls the same lighting components. The following list indicates which exterior lighting components the BCM can turn ON:

    • The low beams and park lamps
    • The high beams
    • The daytime running lamps
    • The front fog lamps
    • The rear fog lamps (export only)

Interior Lighting Control

The BCM can turn ON some of the interior lighting independently of the interior lighting system. The vehicle lighting system controls the same lighting components. The BCM controls the following interior lamps:

    • The courtesy lamps
    • The illuminated entry control of the courtesy lamps
    • The vanity lamp is activated.
    • The courtesy lamp is activated.
    • The dome lamps
    • The glove compartment lamp
    • The reading lamps
    • The inside rearview mirror lamps

The courtesy lamps are enabled by the following inputs:

    • Discrete input to the BCM from the following components:
       - The door jamb switches
       - The door handle
       - The dome lamp
    • RFA transmitter activation (function of illuminated entry).

Segment Inspection

The IPC illuminates in order to verify that all of the segments of the telltale displays are operating correctly. The turn signal indicators do not turn ON during this inspection. Do not attempt further diagnosis unless all of the segments appear. Further diagnosis could lead to misdiagnosis. If any portions or segments of the IPC displays are inoperative, first diagnose the IPC.