GM Service Manual Online
For 1990-2009 cars only

Body Control Module (BCM)

Scan Tool Parameter

System State

Expected Value

Definition

Operating Conditions: Ignition ON/Engine OFF/Vehicle in PARK/Park Brake Released/Headlamps in AUTO/All Doors Closed

A/C Request

--

Yes

The scan tool displays Yes/No. Yes is displayed when the body control module (BCM) receives an input from the HVAC control assembly for an A/C request. No is displayed when there is no A/C request.

Accy. Relay Command

--

On

The scan tool displays the commanded state of the retained accessory power (RAP) relay. The scan tool displays ON when the body control module (BCM) provides ground to the RAP relay control circuit.

Ambient Light Sensor

--

1.75 Volts Maximum Light to 4.9 Volts Maximum Dark

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.

Auto Learn Timer

--

0-600

The scan tool displays the time in seconds used by the BCM to learn valid code from the Passlock™ sensor using the techline terminal reprogramming procedure.

Battery Voltage Signal

--

Varies

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

Battery Voltage

--

12.5

The scan tool displays 8-14 volts. The amount of battery voltage available at the body control module (BCM).

Brake Fluid Level Sensor

--

OK

The scan tool displays Low/OK. This is the state of the brake fluid level.

BTSI Output

--

Off

The scan tool displays OFF/On. On is displayed if the BCM senses a brake transmission shift interlock.

Cargo Lamp Switch

--

Inactive

The scan tool displays the position of the cargo lamp switch. The scan tool displays ACTIVE when the switch is pressed. The BCM uses this data in controlling the operation of the cargo lamp.

Content Theft State

--

Off

The scan tool displays the current content theft deterrent (CTD) state.

Courtesy Lamp Output

--

Off

The scan tool displays the commanded state of the BCM to activate the courtesy lamps. The scan tool displays ON when the BCM energizes the courtesy lamps supply voltage circuit to illuminate the courtesy lamps.

Courtesy Lamp Switch

--

Inactive

The scan tool displays the position of the courtesy lamp switch. The scan tool displays ACTIVE when the switch is activated. The BCM uses this data in controlling the operation of the courtesy lamps.

Crank Voltage

--

4.4

This parameter displays the voltage read by BCM, through Ignition Off/Run/Crank signal.

Dimming Potentiometer

--

Varies

The scan tool displays the voltage value indicating the position of the I/P dimmer switch. 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.

Dome Lamp Override Switch

--

Off

The scan tool displays the position of the dome override switch. The scan tool displays On when the switch is pressed. The BCM uses this data in controlling the operation of the courtesy lamps.

Door Lock Output

--

Off

The scan tool displays On/Off. This input displays On when the remote keyless entry transmitter lock button is pressed.

Door Lock Relay Fdbk.

--

Off

The scan tool displays Active/Inactive. The door lock relay feedback input to the BCM, where the relay being actuated is displayed as Active.

Door Unlock Output

--

Off

The scan tool displays On/Off. This input displays On when the remote keyless entry transmitter unlock button is pressed.

Driver Door Ajar Sw.

--

Door Closed

The scan tool displays the position of the driver door ajar switch. The scan tool displays Door Closed when the door is closed and Door Ajar when the door is open or ajar. The BCM uses this data in controlling the operation of the courtesy lamps and door ajar warning.

DRL Status

--

Varies

The scan tool displays the commanded state of the daytime running lamps (DRL). The scan tool displays ON when the BCM activates the DRL mode.

Fog Lamp Relay Cmd.

--

Off

The scan tool displays the commanded state of the fog lamp relay. The scan tool displays ON when the BCM energizes the fog lamp relay to activate the fog lamps.

Front Fog Lamp Switch

--

Inactive

The scan tool displays the position of the front fog lamp switch. The scan tool displays ACTIVE when the switch is pressed. The BCM uses this data in controlling the operation of the front fog lamps.

Front Wipers Active

--

No

The scan tool displays the position of the park brake pedal. The scan tool displays Applied when the park brake is engaged closing the switch. The BCM uses this data in controlling the operation of the park brake indicator, the reminder chime feature and the DRL system.

Hazard Lamp Switch

--

Inactive

The scan tool displays the position of the hazard lamp switch. The scan tool displays ACTIVE when the switch is pressed. The BCM uses this data in controlling the operation of the hazard lamps.

Headlamp On Switch

--

Inactive

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.

Headlamp Off Switch

--

Inactive

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.

Headlamp Relay

--

Varies

The scan tool displays the commanded state of the headlamp relay. The scan tool displays ON when the BCM grounds the headlamp relay to activate the headlamps.

High Beam Select Switch

--

Inactive

The scan tool displays the position of the high beam select switch. The scan tool displays Active when the switch is used to activate the high beams.

High Beam Relay Command

--

Off

The scan tool displays the commanded state of the high beam relay. The scan tool displays On when the BCM has activated the high beam relay to illuminate the high beam headlamps.

Horn Relay Command

--

Off

The scan tool displays On/Off to indicate the current state of the horn relay as commanded by the body control module (BCM) or the horn switch.

Ignition Accessory

--

Active

The scan tool displays Active or Inactive. This is the state of the ignition accessory

Ignition Off/Run/Crank

--

Active

The scan tool displays the position of the ignition switch. The scan tool displays Active when the ignition switch is in the RUN or CRANK position.

Ignition 1 Run/Crank

--

Active

The scan tool displays the position of the ignition switch. The scan tool displays Active when the ignition switch is in the RUN or CRANK position.

Ignition 3

--

Active

The scan tool displays the state of the Ignition 3 output.

Inadv Power Cmd1

--

On

The scan tool displays On or Off. 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.

Inadv Power Cmd 2

--

On

The scan tool displays On or Off. 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.

LF Pressure Sensor ID

--

Numeric

The scan tool displays a number up to 8 digits in length, or an asterisk. A number displayed indicates the tire pressure sensor unique identification (Id) code, and that it has been learned into the BCMs memory.

LF Pressure Sensor Mode

--

Stationary

Stationary indicates the sensors internal roll switch is open and the sensor has made its stationary transmission which occurs once every 60 minutes from the last stationary transmission. Wake indicates the sensor is transitioning to drive mode, in this mode the sensor has detected an initial roll switch closure. Drive indicates the sensors roll switch has been closed for at least 10 seconds and the sensor is transmitting once every 60 seconds. Re-Measure indicates the sensor has detected a 1.6 psi change in tire pressure. Learn indicates the sensor has been activated by a low frequency transmission. Low Bat indicates the sensor's internal battery charge level is low. N/A indicates the sensor is in a mode not supported by the scan tool.

LF Tire Pressure

--

35 psi

The scan tool displays 0-344 kPa (0-51 psi). The actual pressure of the front tire.

LF Turn/Hazard Lamp Command

--

Off

The scan tool displays the commanded state of the left front turn/hazard lamp. The scan tool displays ON when the BCM activates the left front turn/hazard supply voltage circuit.

LR Pressure Sensor ID

--

Numeric

The scan tool displays a number up to 8 digits in length, or an asterisk. A number displayed indicates the tire pressure sensor unique identification (Id) code, and that it has been learned into the BCMs memory.

LR Pressure Sensor Mode

--

Stationary

Stationary indicates the sensors internal roll switch is open and the sensor has made its stationary transmission which occurs once every 60 minutes from the last stationary transmission. Wake indicates the sensor is transitioning to drive mode, in this mode the sensor has detected an initial roll switch closure. Drive indicates the sensors roll switch has been closed for at least 10 seconds and the sensor is transmitting once every 60 seconds. Re-Measure indicates the sensor has detected a 1.6 psi change in tire pressure. Learn indicates the sensor has been activated by a low frequency transmission. Low Bat indicates the sensor's internal battery charge level is low. N/A indicates the sensor is in a mode not supported by the scan tool.

LR Tire Pressure

--

35 psi

The scan tool displays 0-344 kPa (0-51 psi). The actual pressure of the rear tire.

LR Turn/Hazard Lamp Command

--

Off

The scan tool displays the commanded state of the left rear turn/hazard lamp. The scan tool displays ON when the BCM activates the left rear turn/hazard supply voltage circuit.

No Of Fobs Programmed

--

Varies

The scan tool displays key fobs from 1-4.

Passenger Door Ajar Sw.

--

Door Closed

The scan tool displays the position of the passenger door ajar switch. The scan tool displays Door Closed when the door is closed and Door Ajar when the door is open or ajar. The BCM uses this data in controlling the operation of the courtesy lamps and door ajar warning.

Passlock State

--

Normal Decision

The scan tool displays the state of the Passlock™ system power.

Park Lamps Signal

--

Varies

The scan tool displays the commanded state of the park lamp relay. The scan tool displays ON when the BCM activates the park lamp relay to illuminate the park lamps.

Park Lamp Switch

--

Off

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.

Park Brake Switch

--

Released

The scan tool displays the position of the park brake pedal. The scan tool displays Applied when the park brake is engaged closing the switch. The BCM uses this data in controlling the operation of the park brake indicator, the reminder chime feature and the DRL system.

RF Pressure Sensor ID

--

Numeric

The scan tool displays a number up to 8 digits in length, or an asterisk. A number displayed indicates the tire pressure sensor unique identification (Id) code, and that it has been learned into the BCMs memory.

RF Pressure Sensor Mode

--

Stationary

Stationary indicates the sensors internal roll switch is open and the sensor has made its stationary transmission which occurs once every 60 minutes from the last stationary transmission. Wake indicates the sensor is transitioning to drive mode, in this mode the sensor has detected an initial roll switch closure. Drive indicates the sensors roll switch has been closed for at least 10 seconds and the sensor is transmitting once every 60 seconds. Re-Measure indicates the sensor has detected a 1.6 psi change in tire pressure. Learn indicates the sensor has been activated by a low frequency transmission. Low Bat indicates the sensor's internal battery charge level is low. N/A indicates the sensor is in a mode not supported by the scan tool.

RF Tire Pressure

--

35 psi

The scan tool displays 0-344 kPa (0-51 psi). The actual pressure of the front tire.

RF Turn/Hazard Lamp Command

--

Off

The scan tool displays the commanded state of the right front turn/hazard lamp. The scan tool displays ON when the BCM activates the right front turn/hazard supply voltage circuit.

RR Pressure Sensor ID

--

Numeric

The scan tool displays a number up to 8 digits in length, or an asterisk. A number displayed indicates the tire pressure sensor unique identification (Id) code, and that it has been learned into the BCMs memory.

RR Pressure Sensor Mode

--

Stationary

Stationary indicates the sensors internal roll switch is open and the sensor has made its stationary transmission which occurs once every 60 minutes from the last stationary transmission. Wake indicates the sensor is transitioning to drive mode, in this mode the sensor has detected an initial roll switch closure. Drive indicates the sensors roll switch has been closed for at least 10 seconds and the sensor is transmitting once every 60 seconds. Re-Measure indicates the sensor has detected a 1.6 psi change in tire pressure. Learn indicates the sensor has been activated by a low frequency transmission. Low Bat indicates the sensor's internal battery charge level is low. N/A indicates the sensor is in a mode not supported by the scan tool.

RR Tire Pressure

--

35 psi

The scan tool displays 0-344 kPa (0-51 psi). The actual pressure of the rear tire.

RR Turn/Hazard Lamp Command

--

Off

The scan tool displays the commanded state of the right rear turn/hazard lamp. The scan tool displays ON when the BCM activates the right rear turn/hazard supply voltage circuit.

Security Indicator Command

--

Off

The scan tool displays On or Off. This is the state of the security indicator as commanded by the BCM.

Selected Front Tire Pressure

--

35 psi

The scan tool displays the front tire pressure that was last selected for the vehicle.

Selected Rear Tire Pressure

--

35 psi

The scan tool displays the rear tire pressure that was last selected for the vehicle

Selected Tire Type

--

P-Metric Standard

The scan tool displays P-Metric Standard, P-Metric Extended, Load Range C, Load Range D, Load Range E. The tire type that was last selected for the vehicle.

Sensor Learn Mode

--

Inactive

The scan tool displays Active, or Inactive. Active indicates the Tire Pressure Monitor (TPM) systems tire pressure sensor learn mode is active and able to learn all 4 sensor Id codes. Inactive indicates the TPM system is not able to learn the sensor Id codes.

Tamper Time

--

0-600

The scan tool displays the time in seconds remaining before a tamper status is cleared.

TCS Switch State

--

Released

The scan tool displays Released/Pressed. The scan tool will display the state of the Traction Control Switch.

TPM System Enabled

--

Yes

The scan tool displays Yes, or No. Yes indicates the TPM option has been enabled in the body control module (BCM). No indicates the TPM option has not been enabled in the BCM.

Traction Switch LED

--

OFF

The scan tool displays OFF/ON. This will display the state of the traction switch led.

Washer Switch

--

Off

The body control module (BCM) uses this input to determine if the wash switch is pressed. If it is pressed, the BCM commands the wiper micro relay ON and keeps it ON until 2 wipe cycles have completed after the switch has been released.

Wiper Delay Input

--

0

The BCM uses this input to determine if it should command the wiper micro relay ON, and the length of the delay between wipes. The scan tool displays 0 volts when the windshield wiper switch is OFF.

Wiper Relay Cmd.

--

0

This output displays whether or not the BCM, or any other voltage source, is providing voltage for the wiper micro relay. ON is displayed when the BCM detects voltage on the windshield wiper switch signal 2 circuit.

VTD Fuel Disable

--

Inactive

The scan tool displays the state of which the fuel delivery system is in. The scan tool will display ACTIVE when the VTD is in fuel disable.


Body Control Module Scan Tool Output Controls

Scan Tool Output Control

Description

Blower Motor Relay

Turns ON and OFF the blower motor relay.

Brake to Shift Relay

Commands the brake to shift relay ON for 5 seconds and OFF.

Courtesy Lamps

The BCM activates the interior courtesy lamps when you select ON. The interior courtesy lamps remain illuminated for 5 seconds.

Door Lock

The body control module (BCM) actuates all of the door lock actuators for approximately 5 seconds when you select On. All of the doors should lock.

Front Fog Lamps

The BCM activates the front fog lamp relay illuminating the front fog lamps when you select ON. The front fog lamps remain illuminated for 5 seconds.

Gauge LED

The BCM activates the gauge LED lamps when you select ON.

Headlamps

The BCM activates the headlamp relay illuminating the low beam headlamps when you select ON. The low beam headlamps remain illuminated for 5 seconds.

High Beams

The BCM activates the beam select relay illuminating the high beam headlamps and high beam indicator when you select ON while the low beam headlamps are on. The high beam headlamps and indicator remain illuminated for 5 seconds.

Horn

The body control module (BCM) activates the horn momentarily when you select On.

Inadvertent Power 1

The BCM disables the inadvertent power supply circuit when you select OFF. The inadvertent power supply circuit remains disabled for 5 seconds.

Inadvertent Power 2

The BCM disables the inadvertent power supply circuit when you select OFF. The inadvertent power supply circuit remains disabled for 5 seconds.

LF Turn Lamp/DRL

The BCM activates the left front turn/DRL lamp when you select ON. The left front turn/DRL lamp remains activated until commanded OFF.

LR Stop/Turn Signal Lamp

The BCM activates the left rear stop/turn signal lamp and left turn indicator when you select ON. The left rear stop/turn signal lamp and indicator remain activated until commanded OFF.

Parking Lamps

The BCM activates the park lamp relay illuminating the parking lamps when you select ON. The parking lamps remain illuminated for 5 seconds.

Rear Defogger Relay

The BCM activates the rear defog relay when you select ON.

Retained Accessory Power

Commands RAP relay On/Off for 5 seconds to check equipment response

RF Turn Lamp/DRL

The BCM activates the right front turn/DRL lamp when you select ON. The right front turn/DRL lamp remains activated until commanded OFF.

RR Stop/Turn Signal Lamp

The BCM activates the right rear stop/turn signal lamp and right turn indicator when you select ON. The right rear stop/turn signal lamp and indicator remain activated until commanded OFF.

Security Lamp

The BCM actuates the security LED when you select ON. The security LED should illuminate until commanded OFF.

Traction Switch LED

The BCM activates the Traction switch LED when you select ON.

Unlock Doors

The BCM actuates all of the door lock actuators for approximately 5 seconds when you select On. All of the doors should unlock.

Wiper Relay

This output control commands the wiper micro relay ON and OFF. The wiper motor will operate at low speed when the wiper micro relay is ON.