GM Service Manual Online
For 1990-2009 cars only
Table 1: Exterior Lamps
Table 2: Interior Lamps
Table 3: Switch Inputs

Exterior Lamps

Scan Tool Parameter

Units Displayed

Typical Data Value

Ignition On, Engine Off

Ambient Light Sensor

Volts

0.4-4 volts

Battery 1

Volts

Battery Voltage

DRL Relay Command

On/Off

On when requested

DRL Relay Feedback

High/Low

Low when requested

Fog Lamp Relay Cmd.

On/Off

On when requested

Fog Lamp Relay Fdbk.

High/Low

Low when requested

Fog Lamp Switch

On/Off

On when requested

High Beam Switch

On/Off

On when requested

Low Beam Input

Volts

0.4 volts - Battery Voltage

Low Beam Input = Off

Yes/No

Yes when Low Beams requested

Low Beam Input = DRL

Yes/No

Yes when DRL requested

Low Beam Input = High

Yes/No

No when Low Beams requested

Parklamp Switch

On/Off

On when Park Lamps requested

Interior Lamps

Scan Tool Parameter

Units Displayed

Typical Data Value

Ignition On, Engine Off

Battery 1

Volts

Battery Voltage

Dome Lamp Command

On/Off

On when Dome requested

Dome Lamp Feedback

High/Low

Low when Dome requested

Driver Door Switch

High/Low

Low with Driver Door Open

Inadvertent Power Cmd.

On/Off

On

Inadvertent Power Fdbk.

High/Low

High when On

Key In Ignition

Yes/No

Yes

Pass Door Switches

High/Low

Low with any Door Open

Switch Inputs

Scan Tool Parameter

Units Displayed

Typical Data Value

Ignition On, Engine Off

Liftgate Ajar Switch

High/Low

Low with Liftgate Open

Park Brake Switch

On/Off

Off