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 Running

Battery Voltage Signal

Data

Volts

13.9 Volts

Ignition Mode Switch

Data

IDLE / ACC / OFF / CRANK

IDLE

Engine Control Module (ECM)

Scan Tool Parameter

Data List

Units Displayed

Typical Data Value

Ignition ON/Engine OFF

Crank Request Signal

Engine Electrical

Yes/No

No

GEN F-Terminal Signal

Engine Electrical

%

%

GEN L-Terminal Signal Command

Engine Electrical

On/Off

Off

GEN L-Terminal Circuit Status

Engine Electrical

Incomplete / Short Gnd / Open / Short to B+ / OK

OK

Ignition 1 Signal

Engine Electrical

Volts

Varies

PNP Switch

Engine Electrical

Park / Neutral / In Gear

Park

Starter Relay Command

Engine Electrical

On/Off

Off

Starter Relay Circuit Status

Engine Electrical

Incomplete / Short Gnd / Open / Short to B+ / OK

OK

Sensing Diagnostic Module (SDM)

Scan Tool Parameter

Data List

Units Displayed

Typical Data Value

Ignition ON/Engine Running

Battery Voltage Signal

Data

Volts

13.9 Volts

Transmission Control Module (TCM)

Scan Tool Parameter

Data List

Units Displayed

Typical Data Value

Ignition ON/Transmission in Park

IMS

Data

Park, Park/Reverse, Reverse, Reverse/Neutral, Neutral, Neutral/Drive 4, Drive 4, Drive 4/Drive 3, Drive 3, Drive 3/Drive 2, Drive 2, Drive 2/Drive 1, Drive 1, INVALID, OPEN

Park