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Ask Chad Farhat Your Own Question
Chad Farhat
Chad Farhat, ASE Certified Technician A6 - Electrical / Electronic systems A7 Heating / Air conditioning systems
Category: Buick
Satisfied Customers: 3228
Experience:  Owner at Carolina Auto Service & Sales , 20 years Experience in Foreign & Domestic vehicles
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My head lights want come on only the fog lights the car

Customer Question

My head lights want come on only the fog lights the car still runs
JA: Have you checked the fuses? Have you checked the bulbs?
Customer: where would I find the fuses box
JA: What is the model/year of your Buick?
Customer: It's a 06 Buick Rendezvous
JA: Are you fixing your Rendezvous yourself? What have you tried so far?
Customer: I haven't tried anything yet. Back in April the computer was replaced so I was thinking it had something to do with that
JA: Anything else you want the mechanic to know before I connect you?
Customer: no
Submitted: 7 months ago.
Category: Buick
Expert:  Chad Farhat replied 7 months ago.

Hi, I'm Chad. Welcome to JustAnswer. I'm reviewing your question and I will be posting your reply ASAP.

Expert:  Chad Farhat replied 7 months ago.

hey how are you

1- the headlight switch will be next to check.

2- but like you mentioned that the computer was replaced already and usually that is the issue,did they tell you they changed the BCM (Body control Module)

last time in april

Please let me know

Thank You

Chad Farhat

ASE Certified Technician

Customer: replied 7 months ago.
Where would i find the headlight switch
Expert:  Chad Farhat replied 7 months ago.

it will be labeled #1 in the diagrams i just sent you

press on the blue link to open the picture

Expert:  Chad Farhat replied 7 months ago.

Please review the description of the system below

EXTERIOR LIGHTING SYSTEMS DESCRIPTION AND OPERATION EXTERIOR LAMPS The exterior lighting consist of the following lamps: - The headlamps - The daytime running lamps (DRL) - The fog lamps - The park, tail, licence and marker lamps - The turn signal lamps - The stop lamps - The backup lamps HEADLAMPS The headlamps may be turned on two different ways. First, when the driver places the headlamp switch is placed in the ON position, for normal operation. Second, with the headlamp switch placed in the OFF position, for automatic lamp control (ALC). During ALC control the headlamps will be in day time running lamp (DRL) operation in daylight conditions, or low beam operation in low light conditions. Voltage is applied at all times to the coil side and the switched side of both the HDLP Low Beam relay and the HDLP High Beam relay. When the headlamp switch is in the HEAD position, a ground signal is applied from G201 to the headlamp switch. The headlamp switch supplies the ground circuit to the BCM. The BCM then applies a ground through the headlamp relay control circuit to the headlamp dimmer switch. Depending on the switch position, the ground circuit is applied to the coil side of either the HDLP Low beam relay or the HDLP High beam relay. This energizes the coil and closes the switch. Depending on the headlamp switch position, voltage is then applied through the relay to the Low Beam LT and Low Beam RT Fuse or to the High Beam LT and High Beam RT fuse. Voltage is then supplied to the respected headlamps. The left headlamp receives it ground circuit from G101 and the right headlamp high beam receives it ground circuit from G100. If the headlight switch is left in the ON position, the inadvertent power control feature will turn off the headlights approximately 30 seconds after the ignition switch is turned to the OFF position. If the driver places the headlight switch in the ON position after the ignition switch has been turned OFF, or if the ignition switch is in the ACCY position, the headlights will remain on until turned off or the battery runs dead. HEADLAMPS ON WARNING The radio activates the headlamps on warning as requested by the body control module (BCM). The BCM sends a class 2 message to the radio indicating the chime frequency (fast rate) and duration (continuous). The headlamps on warning sounds when the following occurs: - The ignition is OFF. - The BCM determines that the driver's door is open (signal is low). - The BCM determines that the headlamp switch is in the park or head position. DAYTIME RUNNING LAMPS (DRL) The ambient light sensor is a light sensitive transistor that varies its voltage signal to the body control module (BCM) in response to changes to the outside (ambient) light level. When the BCM receives this signal it will either turn on the daytime running lamps (DRL) or the headlight relay for auto headlamp operation. Any function or condition that turns on the headlights will cancel the daytime running lamps operation. The daytime running lamps (DRL) illuminate the high beam headlights at a reduced intensity. With the headlight switch in the OFF position, the headlights will either be turned ON or OFF, after an approximate 30 second delay depending on whether daylight or low light conditions are sensed. Voltage is applied at all times to both the switched and coil side of the DRL relay. When the ambient light sensor detects a low light condition, the BCM applies a ground to the DRL relay control circuit. This energizes the relay and applies voltage to the DRL fuse. Current flows from the DRL fuse to the right high beam lamp to the left hand high beam lamp. The high beam headlamps are now in series, and split the voltage. The headlamps illuminate at half intensity. The ground is provided from G101. The DRL operate when the ignition switch is in the RUN position, and the parking brake is not set or the transmission is not in park. When these conditions have been met and the ambient light sensor indicates daytime conditions, the DRL will illuminate. FOG LAMPS With the ignition switch in the ON position, and the park lamps or low beam headlights on, the fog lights will illuminate when the driver presses the fog lamp switch. The FOG LPS fuse in the underhood fuse block, supplies battery positive voltage to both the fog lamp relay switch contacts and the fog lamp relay coil circuit. The fog lamp relay coil is controlled by the body control module (BCM). When the fog lamp switch is pressed, the BCM fog lamp switch input is grounded. The BCM will then energize the fog lamp relay coil control circuit. The current flow is now from the fog lamp relay to both front fog lamps and to ground G100 and G101. The state of the fog lamps either ON or OFF will remain the same until the front fog lamp switch is pressed again, or the ignition switch is cycled OFF and ON. The park lamps or low beam headlights must be ON in order for the fog lights to be illuminated. Fog lamp operation will be cancelled whenever the park lamps, are turned OFF or the high beam headlights have been selected. PARK, TAIL AND MARKER LAMPS The park, tail and marker lamps, including the license lamps, are turned on when the headlamp switch is placed in either the PARK or HEADLAMP position, or anytime the headlights are requested. The PARK LPS fuse in the underhood fuse block, supplies battery positive voltage to both the park lamp relay switch contacts and park lamp relay coil circuit. The park lamp relay coil is controlled by the body control module (BCM). When the headlamp switch is placed in the PARK position, the BCM will then energize the park lamp relay coil control circuit. Current flow is now from the park lamp relay to the park/tail lamps. The front park lamps are grounded at G100 and G101. The rear park lamps are grounded at G401 and G402. The license plate lamps are a part of the rear park lamp circuit and are grounded at G401. The inadvertent power control feature prevents the park lights from remaining on more than 10 minutes if left on. If the park lights are turned on after the ignition switch has been turned OFF, or is in the ACCY position, they will remain on until turned off or the battery runs dead. REMOTE KEYLESS ENTRY EXTERIOR LAMP ILLUMINATION When the remote function actuation (RFA) module receives a door unlock command from the remote function actuator transmitter, the RFA module will ground the door unlock signal circuit to the BCM, [send a class 2 message to the body control module (BCM), indicating that an UNLOCK command has been received. The BCM will then flash the park lamps twice. With all the doors closed, and the RKE transmitter is used to lock the doors, the park lamps will flash twice. The park lamps will not flash if the rear compartment is opened using the RKE transmitter. TURN SIGNAL LAMPS Ignition positive voltage from the TRN SIG fuse in the console fuse block is supplied to the turn signal switch. when the turn signal lever is placed in the turn left or turn right position, voltage is applied to the turn signal lamp flasher assembly in the console fuse block. The turn signal lamps may only be activated with the ignition switch in the ON or ACCY position. When the turn signal switch is placed in either the left or right position, current flow is from the flasher module's output to the turn signal switch assembly. The flasher module then sends an on-off voltage signal to either the left or right turn signals and their instrument cluster (IPC) indicator. For the hazard lamps voltage is applied from the HZDL fuse in the console fuse block to the hazard flasher. When the hazard switch is pressed, all the turn signal lamps will flash including both IPC turn signal indicators. The hazard and turn signal lamp flasher assembly is grounded at G200. The front turn signals are grounded at G100 and G101 and the rear turn signals are grounded at G401 and G402. TURN SIGNAL REMINDER The radio activates the turn signal warning as requested by the IPC. The IPC sends a class 2 message to the radio indicating the chime frequency (medium rate) and duration (continuous). The turn signal warning sounds when the following occurs: - The ignition switch is in the RUN position. - The turn signal switch is in either turn position, sensing, within 1 second, an open to B+ transition in the turn signal control circuit (left or right turn). - The vehicle has traveled a distance of 1.2 km (3/4 mi) by counting pulses on the vehicle speed input circuit. The IPC turns off the turn signal reminder when either the ignition switch is turned to the OFF position, or the turn signal switch returns to the OFF position, sensing, within 1 second, no transitions from open to B+ in either of the turn signal control circuits (left turn or right turn). STOP LAMPS The HZDL fuse in the console fuse block supplies battery positive voltage to the normally open stoplamp switch. When the driver presses the brake pedal, the switch contacts close and battery positive voltage is supplied to both left and right stop lamp assemblies and to the center high mounted stop lamp (CHMSL). The CHMSL is grounded at G301. The left stop lamp is grounded at G401 and the right stop lamp is grounded at G402. BACKUP LAMPS The TURN SIG fuse in the console fuse block supplies battery positive voltage to park neutral position switch. When the gear selector lever is in the REVERSE position, power is supplied to both of the backup lamps. The backup lamps are grounded at G401 and G402. BATTERY RUNDOWN PROTECTION / INADVERTENT POWER The body control module (BCM) controls the lighting system through circuits that enable both the exterior lamp functions of the park lamps, the headlamps , and the fog lamps, as well as the interior lamps. The BCM opens these enabling circuits 20 minutes after the ignition switch is turned OFF with no lamp switch activity. If the ignition switch is turned to any position other than OFF, or if a lamp switch is activated during this 20-minute period, the timer resets for another 20 minutes. LIGHTING SYSTEM INDICATORS High Beam The instrument panel cluster (IPC) illuminates the high beam indicator when the body control module (BCM) detects that the high beams are requested. The IPC receives a class 2 message from the BCM requesting illumination. Park Lamp Out The IPC illuminates the park lamp out indicator in the message center when the BCM determines a park lamp out condition exists. The IPC receives a class 2 message from the BCM requesting illumination. The IPC sends a class 2 message to the radio in order to activate an audible warning. Turn Signals The IPC illuminates the right or left turn signal indicator when the IPC detects a turn signal request or a hazard request. If the IPC determines that the turn signal is active for more than 1.21 km (0.75 mi), the IPC sends a class 2 message to the radio in order to activate the audible warning.

Expert:  Chad Farhat replied 7 months ago.

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Thank You
Chad Farhat
ASE Certified Technician

Expert:  Chad Farhat replied 6 months ago.

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Chad Farhat
ASE Certified Tedchnician