GM Service Manual Online
For 1990-2009 cars only

Body Control Module (BCM)

Scan Tool Parameter

Data List

Units Displayed

Typical Data Value

Ignition ON/Engine OFF/Vehicle in PARK/Park Brake RELEASED/Headlamps in AUTO/All Doors/Tailgate Closed

Battery Voltage

Data

Volts

Varies

Light Sensor

Data

Volts

1.75 Volts Maximum Light to 4.9 Volts Maximum Dark

Low Beam Duty Cycle

Data

Percent

0%/81%/100%

Dimming Input

Data

Volts

Varies

Dimming Level

Data

Percent

0%

Backlight Dimming

Data

Percent

Varies

Indicator Dimming

Data

Percent

Varies

Ignition 0

Inputs

On/Off

On

Ignition 1

Inputs

On/Off

On

Ignition 3

Inputs

On/Off

On

Key In Ignition

Inputs

Yes/No

Yes

Left Rear Door Ajar Sw.

Inputs

On/Off

Off

Right Rear Door Ajar Sw.

Inputs

On/Off

Off

Flash to Pass Switch

Inputs

On/Off

Off

Interior Lamp Defeat Switch

Inputs

On/Off

On/Off

Headlamp Switch

Inputs

Active/Inactive

Inactive

Parklamp Switch

Inputs

Active/Inactive

Inactive

High Beam Switch

Inputs

On/Off

Off

Front Wipers Active

Inputs

Yes/No

No

Courtesy Lamp Switch

Inputs

Active/Inactive

Inactive

Front Fog Lamp Switch

Inputs

On/Off

Off

Park Brake Switch

Inputs

Set/Released

Released

Inadvertent Power Relay

Inputs

On/Off

Off

DRL Relay

Outputs

On/Off

Varies

High Beams

Output Control

On/Off

Off

Low Beam Duty Cycle

Output Control

Percent

0%/81%/100%

Park Lamp Relay

Output Control

On/Off

On/Off

Backup Lamps

Output Control

On/Off

Off

Dimming Level

Output Control

Percent

Varies

Inadvertent Power Relay

Output Control

On/Off

On

Driver Door Module (DDM)

Scan Tool Parameter

Data List

Units Displayed

Typical Data Value

Ignition ON/Engine OFF/Vehicle in PARK/Park Brake RELEASED/Headlamps in AUTO/All Doors/Tailgate Closed

Battery 1

Data

Volts

Varies

Battery 2

Data

Volts

Varies

Dimming Potentiometer

Data

Percent

Varies

Window Switch Backlight

Data

Percent

Varies

Memory Switch Backlight

Data

Percent

Varies

Mirror Switch Backlight

Data

Percent

Varies

Dimming Enable

Inputs

On/Off

On

Door Ajar Switch

Inputs

On/Off

Off

Passenger Door Module (PDM)

Scan Tool Parameter

Data List

Units Displayed

Typical Data Value

Ignition ON/Engine OFF/Vehicle in PARK/Park Brake RELEASED/Headlamps in AUTO/All Doors/Tailgate Closed

Battery 1

Data

Volts

Varies

Battery 2

Data

Volts

Varies

Dimming Potentiometer

Data

Percent

Varies

Window Switch Backlight

Data

Percent

Varies

Memory Switch Backlight

Data

Percent

Varies

Door Ajar Switch

Inputs

On/Off

Off

Liftgate Module (LGM)

Scan Tool Parameter

Data List

Units Displayed

Typical Data Value

Ignition ON/Engine OFF/Vehicle in PARK/Park Brake RELEASED/Headlamps in AUTO/All Doors/Tailgate Closed

Liftgate Ajar Switch

Data

Ajar/Closed

Closed

Liftglass Ajar Switch

Data

Ajar/Closed

Closed

Battery Voltage

Data

Volts

Varies