Circuit/System Description
The INT LIGHT fuse supplies battery voltage to the inadvertent load control relay located in the body control module (BCM). The BCM applies ground to the inadvertent relay control circuit which energizes the inadvertent load control relay coil. With the relay coil energized, the switch contacts close allowing battery voltage to flow from the INT LIGHT fuse to the inside rearview mirror lamps through the inside rearview mirror lamps supply voltage circuit. The inside rearview mirror lamps are controlled by a 3 position (OFF, DOOR, ON) switch. When the inside rearview mirror switch is placed in the DOOR position, the lamps are controlled by the BCM by grounding the courtesy lamp control circuit. When any door is opened, the jam switch contacts close and the BCM receives a door-open input. If the BCM receives a door lock or unlock input, the BCM will activate the inadvertent relay control circuit, providing battery voltage to the inside rearview mirror lamps. The BCM also provides ground to the inside rearview mirror lamps through the courtesy lamp control circuit.
When the fog lamp switch is placed in the ON position, ground is applied through the fog lamp switch signal circuit at G305 to the body control module (BCM). The BCM applies battery voltage through the fog lamp relay control circuit to the coil side of the fog lamp relay and the fog lamps ON indicator located on the fog lamp switch. Battery voltage is applied at all times from the FOG LP fuse to the switch side of the fog lamp relay. When the relay coil is energized, the relay switch contacts close and allow battery voltage to be applied from the FOG LP fuse, through the relay switch contacts, to the fog lamps. Ground for the fog lamps is applied at all times at G102 for the left fog lamp and G101 for the right fog lamp. G102 also serves as ground for the coil side of the fog lamp relay.
The INT LIGHT fuse supplies battery voltage to the inadvertent load control relay located in the body control module (BCM). The BCM applies ground to the inadvertent relay control circuit which energizes the inadvertent load control relay coil. With the relay coil energized, the switch contacts close allowing battery voltage to flow from the INT LIGHT fuse to the inside rearview mirror lamps through the inside rearview mirror lamps supply voltage circuit. The inside rearview mirror lamps are controlled by a 3 position (OFF, DOOR, ON) switch. When the inside rearview mirror switch is placed in the DOOR position, the lamps are controlled by the BCM by grounding the courtesy lamp control circuit. When any door is opened, the jam switch contacts close and the BCM receives a door-open input. If the BCM receives a door lock or unlock input, the BCM will activate the inadvertent relay control circuit, providing battery voltage to the inside rearview mirror lamps. The BCM also provides ground to the inside rearview mirror lamps through the courtesy lamp control circuit.
With the headlamp switch in the HEAD position, the headlamp switch headlamp ON signal circuit is grounded through the turn signal/multifunction switch at G305. In response to this input, the body control module (BCM) provides ground to either the headlamp low beam relay control circuit through the headlamp switch signal circuit or the headlamp high beam relay control circuit. The position of the headlamp dimmer switch determines which relay coil has ground. The BCM supplies ground to the relay coil circuits, if the headlamps are necessary. The LO BEAM and HI BEAM relays are supplied with battery positive voltage at there coil and switch input circuits. When the low beam relay coil is energized, current flows through the LH LOW and the RH LOW fuses to the low beam headlamps. When the headlamp high beam relay coil is energized, current flows through the LH HIGH and the RH HIGH fuses to the high beam headlamps. The headlights may be switched to high beam with the movement of the headlamp dimmer switch lever. With the headlamp dimmer switch in the high beam position the BCM sends a message via GMLAN to the instrument panel cluster (IPC) requesting the IPC to illuminate the high beam indicator. Ground for the left headlamp assembly is provided at G102. Ground for the right headlamp assembly is provided at G101.
The body control module (BCM) receives an input from the instrument panel (I/P) dimmer switch. The BCM provides the I/P dimmer switch with voltage and a low reference. The I/P dimmer switch is a potentiometer that varies the input signal voltage to the BCM. This input determines the intensity level of the backlighting illumination. The driver may change intensity of the backlighting by positioning the I/P dimmer switch between the minimum and maximum settings. The BCM will default to full intensity if the input from the I/P dimmer switch is not within the specified values. The backlighting illumination intensity is controlled by the BCM by varying the pulse width modulation (PWM) voltage that feeds the dimming signal circuits of the individual lamps. All interior backlighting lamps are permanently grounded.
The ambient light sensor is used to monitor outside lighting conditions. The ambient light sensor provides a voltage signal that will vary between .2 and 4.9 volts depending on outside lighting conditions. The body control module (BCM) provides a low reference ground and a 5-volt reference signal to the ambient light sensor. The BCM monitors the ambient light sensor signal circuit to determine if outside lighting conditions are correct for either daytime running lights (DRL) or automatic lamp control (ALC) when the headlamp switch is in the AUTO position. In high outside light conditions, the BCM will command the DRLs ON. In low light conditions, when the headlamps switch is in AUTO position, the BCM will command the low beam headlamps ON.
The brake pedal position sensor is used to sense the action of the driver application of the brake pedal. The brake pedal position sensor provides an analog voltage signal that will increase as the brake pedal is applied. The body control module (BCM) provides a low reference signal and a 5-volt reference voltage to the brake pedal position sensor. When the variable signal reaches a voltage threshold indicating the brakes have been applied, the BCM will apply battery positive voltage to the stop lamps, center high mounted stop lamp (CHMSL), transmission control module (TCM), and engine control module (ECM). The stop lamps will not operate unless the ignition is in the ON position.
Ground is applied at all times at G305 to the turn signal/multifunction switch. The turn signal lamps may only be activated with the ignition switch in the ON or START position. When the turn signal/multifunction switch is placed in either the TURN RIGHT or TURN LEFT position, ground is applied to the body control module (BCM) through either the right turn or left turn signal switch signal circuit. Battery voltage is applied at all times from the BATT MAIN 3 fuse to the BCM. The BCM then applies a pulsating voltage to the front and rear turn signal lamps. Ground for the left front turn signal lamp is supplied at G102. Ground for the right front turn signal lamp is supplied at G101. Ground for the left rear turn signal lamp is supplied at G400. Ground for the right rear turn signal lamp is supplied at G402. For more detailed information concerning turn signal lamp operation refer to Exterior Lighting Systems Description and Operation .
Ground is applied at all times at G305 to the turn signal/multifunction switch. The turn signal lamps may only be activated with the ignition switch in the ON or START position. When the turn signal/multifunction switch is placed in either the TURN RIGHT or TURN LEFT position, ground is applied to the body control module (BCM) through either the right turn or left turn signal switch signal circuit. Battery voltage is applied at all times from the BATT MAIN 3 fuse to the BCM. The BCM then applies a pulsating voltage to the front and rear turn signal lamps. Ground for the left front turn signal lamp is supplied at G102. Ground for the right front turn signal lamp is supplied at G101. Ground for the left rear turn signal lamp is supplied at G400. Ground for the right rear turn signal lamp is supplied at G402. For more detailed information concerning turn signal lamp operation refer to Exterior Lighting Systems Description and Operation .
The brake pedal position sensor is used to sense the action of the driver application of the brake pedal. The brake pedal position sensor provides an analog voltage signal that will increase as the brake pedal is applied. The body control module (BCM) provides a low reference signal and a 5-volt reference voltage to the brake pedal position sensor. When the variable signal reaches a voltage threshold indicating the brakes have been applied, the BCM will apply battery positive voltage to the stop lamps, center high mounted stop lamp (CHMSL), transmission control module (TCM), and engine control module (ECM). The stop lamps will not operate unless the ignition is in the ON position.
The brake pedal position sensor is used to sense the action of the driver application of the brake pedal. The brake pedal position sensor provides an analog voltage signal that will increase as the brake pedal is applied. The body control module (BCM) provides a low reference signal and a 5-volt reference voltage to the brake pedal position sensor. When the variable signal reaches a voltage threshold indicating the brakes have been applied, the BCM will apply battery positive voltage to the stop lamps, center high mounted stop lamp (CHMSL), transmission control module (TCM), and engine control module (ECM). The stop lamps will not operate unless the ignition is in the ON position.
The brake pedal position sensor is used to sense the action of the driver application of the brake pedal. The brake pedal position sensor provides an analog voltage signal that will increase as the brake pedal is applied. The body control module (BCM) provides a low reference signal and a 5-volt reference voltage to the brake pedal position sensor. When the variable signal reaches a voltage threshold indicating the brakes have been applied, the BCM will apply battery positive voltage to the stop lamps, center high mounted stop lamp (CHMSL), transmission control module (TCM), and engine control module (ECM). The stop lamps will not operate unless the ignition is in the ON position.
The brake pedal position sensor is used to sense the action of the driver application of the brake pedal. The brake pedal position sensor provides an analog voltage signal that will increase as the brake pedal is applied. The body control module (BCM) provides a low reference signal and a 5-volt reference voltage to the brake pedal position sensor. When the variable signal reaches a voltage threshold indicating the brakes have been applied, the BCM will apply battery positive voltage to the stop lamps, center high mounted stop lamp (CHMSL), transmission control module (TCM), and engine control module (ECM). The stop lamps will not operate unless the ignition is in the ON position.
The brake pedal position sensor is used to sense the action of the driver application of the brake pedal. The brake pedal position sensor provides an analog voltage signal that will increase as the brake pedal is applied. The body control module (BCM) provides a low reference signal and a 5-volt reference voltage to the brake pedal position sensor. When the variable signal reaches a voltage threshold indicating the brakes have been applied, the BCM will apply battery positive voltage to the stop lamps, center high mounted stop lamp (CHMSL), transmission control module (TCM), and engine control module (ECM). The stop lamps will not operate unless the ignition is in the ON position.
The underhood fuse block supplies battery positive voltage to the coil and switch terminals of the backup lamps relay. When the transmission is placed in the REVERSE position, the transmission control module (TCM) sends a message via GMLAN to the body control module (BCM). The message indicates that the gear selector is in the REVERSE position. The BCM grounds the backup lamp relay control circuit which energizes the backup lamps relay. With the relay energized, the switch side contacts close and provide battery voltage to the backup lamps fuse through to the backup lamps. The backup lamps are permanently grounded at G402. With both power and ground the backup lamps illuminate. Once the driver moves the gear selector out of the REVERSE position, a message is sent by the TCM via GMLAN serial data requesting the BCM to remove ground from the backup lamp relay control circuit. This opens the backup lamps relay switch contacts turning OFF the backup lamps.
Battery voltage is applied to the backup lamp switch when the ignition switch is in the RUN or CRANK positions. When the transmission is placed in the REVERSE position, the backup lamp switch provides battery voltage to the backup lamps. The backup lamps are permanently grounded at G402. With both power and ground the backup lamps illuminate. Once the driver moves the gear selector out of the REVERSE position, the backup lamp switch contacts open and the backup lamps turn OFF.
The INT LIGHT fuse supplies battery voltage to the inadvertent load control relay located in the body control module (BCM). The inadvertent load control relay is a non removable relay. The BCM applies ground to the inadvertent relay control circuit which energizes the inadvertent load control relay coil. With the relay coil energized, the switch contacts close allowing battery voltage to flow from the INT LIGHT fuse to the inside rearview mirror lamps through the inside rearview mirror lamps supply voltage circuit. The inside rearview mirror lamps are controlled by a 3 position (OFF, DOOR, ON) switch. When the inside rearview mirror switch is placed in the DOOR position, the lamps are controlled by the BCM by grounding the courtesy lamp control circuit. When any door is opened, the jam switch contacts close and the BCM receives a door-open input. If the BCM receives a door lock or unlock input, the BCM will activate the inadvertent relay control circuit, providing battery voltage to the inside rearview mirror lamps. The BCM also provides ground to the inside rearview mirror lamps through the courtesy lamp control circuit. When the BCM receives a rear hatch open input, the BCM will activate the rear compartment lamp control circuit to provide battery voltage to the rear compartment lamp. The rear compartment lamp is provided ground permanently at G402.
The ambient light sensor is used to monitor outside lighting conditions. The ambient light sensor provides a voltage signal that will vary between .2 and 4.9 volts depending on outside lighting conditions. The body control module (BCM) provides a low reference ground and a 5-volt reference signal to the ambient light sensor. The BCM monitors the ambient light sensor signal circuit to determine if outside lighting conditions are correct for either daytime running lights (DRL) or automatic lamp control (ALC) when the headlamp switch is in the AUTO position. In high outside light conditions, the BCM will command the DRLs ON. In low light conditions, when the headlamps switch is in AUTO position, the BCM will command the low beam headlamps ON.
When the fog lamp switch is placed in the ON position, ground is applied through the fog lamp switch signal circuit at G305 to the body control module (BCM). The BCM applies battery voltage through the fog lamp relay control circuit to the coil side of the fog lamp relay. Battery voltage is applied at all times from the FOG LAMP fuse to the switch side of the fog lamp relay. When the relay coil is energized, the relay switch contacts close and allow battery voltage to be applied from the FOG LAMP fuse, through the relay switch contacts, to the fog lamps. Ground for the fog lamps is applied at all times at G102 for the left fog lamp and G101 for the right fog lamp. G102 also serves as ground for the coil side of the fog lamp relay.
The hazard flashers may be activated in any power mode. The hazard switch is permanently grounded through G305. When the hazard switch is placed in the ON position, ground is applied through the hazard switch signal circuit to the body control module (BCM). The BCM supplies battery voltage to all 4 turn signal lamps in an ON and OFF duty cycle. When the hazard switch is placed in the ON position, the instrument panel cluster (IPC) receives a signal from the BCM via GMLAN requesting both turn signal indicators to be cycled ON and OFF.
With the headlamp switch in the HEAD position, the headlamp switch headlamp ON signal circuit is grounded through the turn signal/multifunction switch at G305. In response to this input, the body control module (BCM) provides ground to either the headlamp low beam relay control circuit through the headlamp switch signal circuit or the headlamp high beam relay control circuit. The position of the headlamp dimmer switch determines which relay coil has ground. The BCM supplies ground to the relay coil circuits, if the headlamps are necessary. The LO BEAM and HI BEAM relays are supplied with battery positive voltage at there coil and switch input circuits. When the low beam relay coil is energized, current flows through the LH LOW and the RH LOW fuses to the low beam headlamps. When the headlamp high beam relay coil is energized, current flows through the LH HIGH and the RH HIGH fuses to the high beam headlamps. The headlights may be switched to high beam with the movement of the headlamp dimmer switch lever. With the headlamp dimmer switch in the high beam position the BCM sends a message via GMLAN to the instrument panel cluster (IPC) requesting the IPC to illuminate the high beam indicator. Ground for the left headlamp assembly is provided at G102. Ground for the right headlamp assembly is provided at G101. For more detailed information concerning headlamp operation refer to Exterior Lighting Systems Description and Operation .
The body control module (BCM) receives an input from the instrument panel (I/P) dimmer switch. The BCM provides the I/P dimmer switch with battery voltage and a low reference. The I/P dimmer switch is a potentiometer that varies the input signal voltage to the BCM. This input determines the intensity level of the backlighting illumination. The driver may change intensity of the backlighting by positioning the I/P dimmer switch between the minimum and maximum settings. The BCM will default to full intensity if the input from the I/P dimmer switch is not within the specified values. The backlighting illumination intensity is controlled by the BCM by varying the pulse width modulation (PWM) voltage that feeds the dimming signal circuits of the individual lamps. All interior backlighting lamps are permanently grounded.
Battery voltage is applied at all times to the coil and switch sides of the PRK LAMPS relay located in the underhood fuse block. Ground is applied at G305 to the turn signal/multifunction switch at all times. When the headlamp switch is placed in either the HEAD or PARK position, ground is applied to the park lamp switch on signal circuit to the body control module (BCM). The BCM reacts to the signal from the park lamp switch by applying ground to the park lamp relay control circuit. This energizes the park lamp relay allowing voltage flows through the PRK LAMPS fuse through the switch contacts of the relay to all park, tail, license, and side marker lamps. Ground for the front park and side marker lamps is supplied at G102 for the left and G101 for the right. Ground for the license and right rear tail lamps is supplied at G400, and the left rear tail lamps at G402.
The INT LIGHT fuse supplies battery voltage to the inadvertent load control relay located in the body control module (BCM). The BCM applies ground to the inadvertent relay control circuit which energizes the inadvertent load control relay coil. With the relay coil energized, the switch contacts close allowing battery voltage to flow from the INT LIGHT fuse to the inside rearview mirror lamps through the inside rearview mirror lamps supply voltage circuit. The inside rearview mirror lamps are controlled by a 3 position (OFF, DOOR, ON) switch. When the inside rearview mirror switch is placed in the DOOR position, the lamps are controlled by the BCM by grounding the courtesy lamp control circuit. When any door is opened, the jam switch contacts close and the BCM receives a door-open input. If the BCM receives a door lock or unlock input, the BCM will activate the inadvertent relay control circuit, providing battery voltage to the inside rearview mirror lamps. The BCM also provides ground to the inside rearview mirror lamps through the courtesy lamp control circuit.
The brake pedal position sensor is used to sense the action of the driver application of the brake pedal. The brake pedal position sensor provides an analog voltage signal that will increase as the brake pedal is applied. The body control module (BCM) provides a low reference signal and a 5-volt reference voltage to the brake pedal position sensor. When the variable signal reaches a voltage threshold indicating the brakes have been applied, the BCM will apply battery positive voltage to the stop lamps, center high mounted stop lamp (CHMSL), transmission control module (TCM), and engine control module (ECM). The stop lamps will not operate unless the ignition is in the ON position. Ground for the left rear stop lamps is provided at G400. Ground for the right rear stop lamps is provided by G402.
Ground is applied at all times at G305 to the turn signal/multifunction switch. The turn signal lamps may only be activated with the ignition switch in the ON or START position. When the turn signal/multifunction switch is placed in either the TURN RIGHT or TURN LEFT position, ground is applied to the body control module (BCM) through either the right turn or left turn signal switch signal circuit. Battery voltage is applied at all times from the BATT MAIN 3 fuse to the BCM. The BCM then applies a pulsating voltage to the front and rear turn signal lamps. Ground for the left front turn signal lamp is supplied at G102. Ground for the right front turn signal lamp is supplied at G101. Ground for the left rear turn signal lamp is supplied at G400. Ground for the right rear turn signal lamp is supplied at G402.