GM Service Manual Online
For 1990-2009 cars only

Data

Backlight Dimming: The scan tool displays the duty cycle of the pulse width modulated (PWM) signal distributed by the body control module (BCM) to the PWM controlled I/P backlighting based on the position of the I/P dimmer switch, thumbwheel. The scan tool displays 0 percent when the headlamp switch is in the AUTO position and the daytime running lamps (DRL) are ON or the I/P dimmer switch is in the FULL DIM position. The scan tool displays approximately 85 percent when either the low beam headlamps or park lamps are activated and the I/P dimmer switch is in the FULL BRIGHT position.

Battery Voltage: The scan tool displays the battery system voltage received by the module.

Dimming Input: The scan tool displays the voltage value indicating the position of the I/P dimmer switch, thumbwheel. The scan tool displays 4 volts when the headlamp switch is in the AUTO position and the daytime running lamps (DRL) are ON or the I/P dimmer switch is in the FULL DIM position. The scan tool displays 0 volts when either the park lamps or the headlamps are turned ON and the I/P dimmer switch is in the FULL BRIGHT position.

Dimming Level: The scan tool displays the duty cycle of the pulse width modulated (PWM) signal distributed by the BCM to the interior lighting circuits. The scan tool displays 0 percent when the interior lamps illumination is OFF. The scan tool displays 100 percent when the interior lamp illumination is at full intensity.

Dimming Potentiometer: The scan tool displays the duty cycle of the pulse width modulated (PWM) signal distributed by the BCM to the PWM controlled door switch backlighting based on the position of the I/P dimmer switch (Thumbwheel). The scan tool displays 0 percent when the headlamp switch is in the AUTO position and the daytime running lamps (DRL) are ON or the I/P dimmer switch is in the FULL DIM position. The scan tool displays 100 percent when either the headlamps or park lamps are activated and the I/P dimmer switch is in the FULL BRIGHT position.

Indicator Dimming: The scan tool displays the duty cycle of the pulse width modulated (PWM) signal distributed by the BCM to the PWM controlled I/P backlighting based on the position of the I/P dimmer switch, thumbwheel. The scan tool displays 1.2 percent when the headlamp switch is in the AUTO position and the daytime running lamps (DRL) are ON or the I/P dimmer switch is in the FULL DIM position. The scan tool displays 100 percent when either the headlamps or park lamps are activated and the I/P dimmer switch is in the FULL BRIGHT position.

Light Sensor: The scan tool displays the output voltage of the ambient light sensor based on the intensity of light detected. As the light intensity increases, the sensor displayed voltage decreases. In the LIGHT state, a low voltage, not less than 1.75 volts, is present and the DRL will be ON. In the DARK state, a high voltage, up to 4.9 volts, is present and the headlamps will be ON.

Inputs

Cargo Door Ajar Switch: The scan tool displays Inactive when the applicable door is fully closed or Active when the door is open or ajar.

Courtesy Lamp Switch: The scan tool displays the position of the courtesy lamp switch. The scan tool displays Active when the switch is turned ON. The BCM uses this data in controlling the operation of the courtesy lamps.

Driver Door Ajar Switch: The scan tool displays Off when the applicable door is fully closed or On when the door is open or ajar.

Flash to Pass Switch: The scan tool displays the position of the flash to pass switch. The scan tool displays On when the switch is pulled to activate the high beams momentarily while the switch is held.

Front Fog Lamp Switch: The scan tool the front fog lamp switch. The scan tool displays ACTIVE or INACTIVE when the switch is depressed. The body control module (BCM) uses this data in controlling the operation of the front fog lamps.

Front Wipers Active: The scan tool displays the state of the wiper motor. The scan tool displays Yes when the wipers are in operation after approximately the first 3 cycles of the wiper blades.

Headlamp Switch: The scan tool displays the position of the headlamp switch. The scan tool displays Active when the headlamp switch is in the ON position. The BCM uses this data in controlling the operation of the headlamps.

High Beam Switch: The scan tool displays the position of the high beam switch. The scan tool displays On when the switch is used to activate the high beams.

Ignition 0: The scan tool displays the position of the ignition switch. The scan tool displays On when the ignition switch is in the RUN or CRANK position.

Ignition 1: The scan tool displays the position of the ignition switch. The scan tool displays On when the ignition switch is in the RUN or CRANK position.

Ignition Accessory: The scan tool displays the position of the ignition switch. The scan tool displays Active when the ignition switch is in the ACCY position only.

Inadvertent Power Relay: The scan tool displays the state of the inadvertent power battery rundown protection feature of the BCM. The scan tool displays On when all inadvertent power circuits are functioning normally.

Interior Lamp Defeat Switch: The scan tool displays the position of the courtesy/dome lamp override switch. The scan tool displays On when the switch is activated requesting the BCM to override the normal interior lamp activation inputs and deactivate the interior lighting.

Key in Ignition: The scan tool displays Yes when the key has been inserted into the ignition switch. The scan tool displays No after the key has been removed.

Left Rear/Rear Cargo Door Switch: The scan tool displays Off when the applicable door is fully closed or On when the door is open or ajar.

Park Lamp Switch: The scan tool displays the position of the park lamp switch. The scan tool displays ON when the park lamp switch is in the ON position. The BCM uses this data in controlling the operation of the park lamps.

Passenger Door Ajar Switch: The scan tool displays Off when the applicable door is fully closed or On when the door is open or ajar.

Right Rear Door Ajar Switch: The scan tool displays Off when the applicable door is fully closed or On when the door is open or ajar.

Outputs

Daytime Running Lamps: The scan tool displays the commanded state of the daytime running lamps (DRL). The scan tool displays ON when the body control module (BCM) allows the DRL relay to activate the DRL.

High Beam Relay: The scan tool displays the commanded state of the high beam relay. The scan tool displays On when the BCM allows the high beam relay to go to ground activating the high beam headlamps.

Low Beam Output: The scan tool displays the commanded state of the low beam relay. The scan tool displays ON when the BCM allows the low beam relay to activate the low beam headlamps.

Park Lamp Relay: The scan tool displays the commanded state of the park lamp relay. The scan tool displays ON when the BCM allows the park lamp relay to activate the park lamps.

Output Control

Backup Lamps: The scan tool displays the commanded state of the body control module (BCM) which directly supplies battery positive voltage to the backup lamps. The scan tool displays On when the BCM activates the backup lamps upon receiving a backup lamp request signal from the backup lamp switch.

Daytime Running Lamps: The scan tool displays the commanded state of the daytime running lamps (DRL). The scan tool displays On when the BCM illuminates the DRL.

Dimming: The scan tool displays the duty cycle of the pulse width modulated (PWM) signal distributed by the BCM to the interior lighting circuits. The scan tool displays 0 percent when the interior lamps illumination is OFF. The scan tool displays 100 percent when the interior lamp illumination is at full intensity.

Inadvertent Power: The scan tool displays the state of the inadvertent power battery rundown protection feature of the BCM. The scan tool displays On when all inadvertent power circuits are functioning normally.

Parking Lamps Relay: The scan tool displays the commanded state of the park lamp relay. The scan tool displays On when the BCM allows the park lamp relay to go to ground to activate the park lamps.