Lighting Systems Buick Century VI

Specifications

Fastener Tightening Specifications

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Begin the system diagnosis with the DIAGNOSTIC SYSTEM CHECK - LIGHTING SYSTEMS . The Diagnostic System Check will provide the following information

1. The identification of the control module(s) which command the system
2. The ability of the control module(s) to communicate through the serial data circuit
3. The identification of any stored diagnostic trouble codes (DTCs) and their status

The use of the Diagnostic System Check will identify the correct procedure for diagnosing the system and where the procedure is located.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. 2. Lack of communication may be due to a partial malfunction of the class 2 serial data circuit or due to a total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.
2. 4. The presence of DTCs which begin with "U" indicate some other module is not communicating. The specified procedure will compile all the available information before tests are performed.

Scheme 69

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BCM Scan Tool Data Definitions

The BCM Scan Tool Data Definitions contains a brief description of all Lighting System related BCM parameters available on the scan tool.

Data List

Ambient Light Sensor: The scan tool displays 2.1 to 4.3 volts. The voltage level varies based upon the amount of light detected by the ambient light sensor. When the sensor detects full bright the scan tool will display 2.1 volts. When low light is detected the scan tool will display 4.3 volts.

Inputs

Courtesy Ground: The scan tool displays Present/Not Present. The input of the courtesy ground is displayed as Not Present when the ground for the courtesy lamps is not detected.

Courtesy Switch: The scan tool displays ON/OFF. The input of the courtesy switch is displayed as ON when the courtesy lamps are command ON.

Headlamp Switch: The scan tool displays inactive or active. When the autolamp switch is in the OFF position, the scan tool will display inactive. When the autolamp switch is in the ON position, the scan tool will display active.

Inadvert. Power Output: The scan tool displays ON/OFF. This output of the BCM is displayed as ON when the Inadvert. power output is present.

LCM lights on Chime: The scan tool displays ON/OFF. The input of the LCM Lights on chime is displayed as ON when the headlamps switch is ON with the ignition off and the key removed.

Lt. Turning Signal Sw.: The scan tool displays Inactive/Active. The input of the Lt. Turning Signal Sw. is displayed as active if the turn signal switch is activated in the turn left position.

Park Brake Switch: The scan tool displays inactive or active. When the park brake is OFF, the scan tool will display inactive. When the park brake is applied, the scan tool will display active.

Rt. Turning Signal Sw.: The scan tool displays Inactive/Active. The input of the Rt. Turning Signal Sw. is displayed as active if the turn signal switch is activated in the turn right position.

Outputs

Backup Lamp Relay: The scan tool displays ON/OFF. This output of the BCM is displayed as ON when the backup lamps are turned on.

Front Fog Lamp Relay: The scan tool displays ON/OFF. This output of the BCM is displayed as ON when the fog lamps are turned on.

Headlamps: The scan tool displays ON/OFF. This output of the BCM is displayed as ON, if the BCM commands the headlamps ON.

Inadvertent Power Output: The scan tool displays OFF or ON. When the BCM is not commanding the inadvertent power On, the scan tool will display Off. When the BCM is commanding the inadvertent power ON, the scan tool will display ON.

Left Turn Signal: The scan tool displays ON/OFF. This output of the BCM is displayed as ON, if the turn signal switch is activated in the turn left position.

Park Lamps: The scan tool displays Off or On. When the BCM is not commanding the park lamp relay On, the scan tool will display Off. When the BCM is commanding the park lamp relay On, the scan tool will display On.

Right Turn Signal: The scan tool displays ON/OFF. This output of the BCM is displayed as ON, if the turn signal switch is activated in the turn right position.

Theater Dimming #1: The scan tool displays OFF or On. When the BCM is not commanding the theater dimming ON, the scan tool displays OFF. When the BCM is commanding the theater dimming ON the scan tool displays ON.

Scheme 72

Circuit Description

The Body Control Module (BCM) uses the courtesy lamps supply voltage circuit as a input circuit and a output circuit. When used as an output circuit the BCM provides battery power to the courtesy lamps. When used as a input circuit the BCM provides an interface to the electrical loads which are controlled by the BCM when the output is inactive. This will allow for determination of the ON/OFF status of the loads.

Conditions for Running the DTC

If the voltage level at the BCM drops to 0.

Conditions for Setting the DTC

1. The fault code sets when the BCM commanded state does not match the feedback. When the courtesy lamps supply voltage circuit is commanded high and a short to ground is present.
2. The fault code also sets when the battery positive voltage circuit of the BCM that is fed by the INADV Power Bus fuse is open or shorted to ground.
3. The condition above must be present for more than 0.1 seconds.

Action Taken When the DTC Sets

The BCM stores DTC B1482 in memory.

Conditions for Clearing the MIL/DTC

1. A current DTC B1482 will clear if voltage is present on the battery positive voltage circuit and the BCM does not detect a short to ground.
2. A history DTC B1482 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present nor any other malfunction in the BCM is detected.
3. The BCM receives a clear code command from the scan tool.

Diagnostic Aids

1. If the DTC B1482 is a history DTC, the fault may be intermittent. Refer to «TESTING FOR INTERMITTENT AND POOR CONNECTIONS»(/buick/century/vi-1997-2005/remont/body-electrical/#wiring-systems__testing-for-intermittent-and-poor-connections) in Wiring Systems.
2. The following conditions may cause an intermittent malfunction to occur: An intermittent short to ground in the courtesy lamps supply voltage circuit. An intermittent open in the battery positive voltage circuit of the BCM that is fed by the INADV Power Bus fuse. The BCM is intermittently shorted to ground.

The numbers below refer to the step numbers on the diagnostic table.

1. 3. Checks the battery positive voltage circuit at the BCM for an open or a short to ground.
2. 4. Checks the courtesy lamps supply voltage circuit for a short to ground. If the fuse in the jumper opens, there is a short to ground in the courtesy lamps supply voltage circuit.

Scheme 73

The fog lamp relay is energized by the fog lamp switch only when the Body Control Module (BCM) has activated the fog lamp enable circuit that supplies the fog lamp switch. The BCM will only activate the fog lamp enable circuit if the following conditions exist

1. The ignition switch must be in the RUN position.
2. The autolamp switch must be in the Park or Headlamp ON position.
3. The autolamp dimmer switch must be in the LOW-BEAM position.

The BCM must be commanding the fog lamp relay to energize.

1. The fault code will set when the fog lamp enable circuit is active and a short to battery voltage is present.
2. The condition above must be present for more than 0.3 seconds.
3. If the short to battery voltage is on the output side of the fog lamp switch, the fault will only set when the fog lamp switch is in the ON position.

The BCM stores DTC B2533 in memory.

Conditions for Clearing the DTC

1. A current DTC B2533 will clear if the short to battery in the fog lamp enable circuit is no longer detected by the BCM.
2. A history DTC B2533 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.
3. The BCM receives a clear code command from the scan tool.

1. If the DTC B2533 is a history DTC, the fault may be intermittent. Refer to «TESTING FOR INTERMITTENT AND POOR CONNECTIONS»(/buick/century/vi-1997-2005/remont/body-electrical/#wiring-systems__testing-for-intermittent-and-poor-connections) in Wiring System.
2. The following conditions may cause an intermittent malfunction to occur: An intermittent short to battery in the fog lamp enable circuit. The fog lamp relay coil is intermittently shorted to battery. The BCM is intermittently shorted to battery.

The numbers below refer to the step numbers on the diagnostic table.

1. 2. Determines that the fault is current when the for lamp relay parameter does not change state.
2. 3. Verifies that there is a short to battery voltage in the fog lamp relay control circuit or related circuits. Not detecting a short to battery voltage would indicate that the fog lamp relay is internally shorted to battery voltage.
3. 4. Test for short to battery voltage internal to the BCM.
4. 5. Test for short to battery voltage on the fog lamps control circuit.

Scheme 74

The Body Control Module (BCM) controls the backup lamp relay. The BCM grounds the backup lamp relay control circuit energizing the backup lamp relay.

Any of the following conditions may be present.

1. The transaxle is not in the reverse position.
2. The emergency vehicle interior lamp switch is enabled.
3. The ignition switch is in the off position.

1. The fault code will set when the backup lamp relay control circuit is inactive and a short to ground or open is present.
2. The condition above must be present for more than 0.3 seconds.

The BCM stores DTC B2552 in memory.

1. A current DTC B2552 will clear if the BCM no longer detects a short to ground or open in the backup lamp relay control circuit.
2. A history DTC B2552 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.
3. The BCM receives a clear code command from the scan tool.

1. If the DTC B2552 is a history DTC, the fault may be intermittent. Refer to «TESTING FOR INTERMITTENT AND POOR CONNECTIONS»(/buick/century/vi-1997-2005/remont/body-electrical/#wiring-systems__testing-for-intermittent-and-poor-connections) in Wiring Systems.
2. The following conditions may cause an intermittent malfunction to occur: An intermittent short to ground or open in the backup lamp control circuit. The backup lamp relay coil is intermittently shorted to ground or open. The BCM is intermittently shorted to ground or open.

The numbers below refer to the step numbers on the diagnostic table.

1. 2. Listen for an audible click when the backup lamp relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
2. 4. Tests for voltage at the coil side of the backup lamp relay. The R/CMPT fuse supplies power to the coil side and the switched side of the backup lamp relay.
3. 5. Verifies that the BCM is providing ground to the backup lamp relay.
4. 6. Tests if ground is constantly being applied to the backup lamp relay.

Scheme 75

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The Body Control Module (BCM) controls the backup lamp relay. The BCM grounds the backup lamps relay control circuit energizing the backup lamp relay.

1. The transaxle must be in the reverse position.
2. The ignition switch must be in the RUN position.
3. The emergency vehicle interior lamp switch is not enabled.

1. The BCM detects a short to battery in the backup lamp relay control circuit when the BCM tries to energize the backup lamp relay.
2. The condition above must be present for more than 0.3 seconds.

The BCM stores DTC B2553 in memory.

1. The BCM no longer detects a short to battery in the backup lamp relay control circuit.
2. A history DTC B2553 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.
3. The BCM receives a clear code command from the scan tool.

1. If the DTC B2553 is a history DTC, the fault may be intermittent. Refer to «TESTING FOR INTERMITTENT AND POOR CONNECTIONS»(/buick/century/vi-1997-2005/remont/body-electrical/#wiring-systems__testing-for-intermittent-and-poor-connections) in Wiring Systems.
2. The following conditions may cause an intermittent malfunction to occur: An intermittent short to battery in backup lamp relay control circuit. The backup lamp relay coil is intermittently shorted to the battery. The BCM is intermittently shorted to the battery.

The numbers below refer to the step numbers on the diagnostic table.

1. 2. Listen for an audible click when the backup lamp relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
2. 3. Verifies that the BCM is providing ground to the backup lamp relay. Indicating a short to voltage internal to the backup lamp relay.
3. 4. Tests for a short to voltage at control circuit of the backup lamp relay.

Scheme 77

The Body Control Module (BCM) receives an ground from the courtesy lamp ground circuit. The sole purpose of this input is to provide a ground path for all of the courtesy lamps controlled through the courtesy lamp low control circuit.

If the input does not match a normal ground potential.

1. The BCM detects a open when a ground is expected.
2. The condition above must be present for more than 0.3 seconds

The BCM stores DTC B2559 in memory.

1. A current DTC B2559 will clear if the open is no longer detected by the BCM.
2. A history DTC B2559 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present nor any other malfunction in the BCM is detected.
3. The BCM receives a clear code command from the scan tool.

1. If the DTC B2559 is a history DTC, the fault may be intermittent. Refer to «TESTING FOR INTERMITTENT AND POOR CONNECTIONS»(/buick/century/vi-1997-2005/remont/body-electrical/#wiring-systems__testing-for-intermittent-and-poor-connections) in Wiring Systems.
2. The following conditions may cause an intermittent malfunction to occur: An intermittent open in the theater dimming ground circuit. The BCM is intermittently opened.

The numbers below refers to the step numbers on the diagnostic table.

1. 3. Checks for an open in the courtesy lamps ground circuit.

Scheme 78

The Body Control Module (BCM) controls the automatic autolamp relay through the autolamp relay control circuit. The BCM grounds the automatic autolamp relay control circuit energizing the autolamp relay.

The BCM must not be commanding the autolamp relay to energize.

1. The BCM detects a short to ground or open in the autolamp relay control circuit when the BCM is not trying to energize the autolamp relay.
2. The condition above must be present for more than 0.3 seconds.

The BCM stores DTC B2577 in memory.

1. A current DTC B2577 will clear if the BCM no longer detects a short to ground or open in the automatic autolamp relay control circuit.
2. A history DTC B2577 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.
3. The BCM receives a clear code command from the scan tool.

1. If the DTC B2577 is a history DTC, the fault may be intermittent. Refer to «TESTING FOR INTERMITTENT AND POOR CONNECTIONS»(/buick/century/vi-1997-2005/remont/body-electrical/#wiring-systems__testing-for-intermittent-and-poor-connections) in Wiring Systems.
2. The following conditions may cause an intermittent malfunction to occur: An intermittent short to ground or open in the automatic autolamp relay control circuit. The autolamp relay coil is intermittently shorted to ground or open. The BCM is intermittently shorted to ground or open.

The numbers below refer to the step numbers on the diagnostic table.

1. 2. Listen for an audible click when the automatic autolamp relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
2. 4. Tests for voltage at the coil side feed of the automatic autolamp relay. The LP Park fuse supplies power to the coil side feed of the automatic autolamp relay.
3. 5. Verifies that the BCM is providing ground to the automatic autolamp relay.
4. 6. Tests if ground is constantly being applied to the automatic autolamp relay.

Scheme 79

Scheme 80

The Body Control Module (BCM) controls the automatic autolamp relay through the autolamp relay control circuit. The BCM grounds the autolamp relay control circuit, energizing the automatic autolamp relay.

The BCM must be commanding the autolamp relay to energize.

1. The BCM detects a short to battery positive voltage in the autolamp relay control circuit when the BCM tries to energize the automatic autolamp relay.
2. The condition above must be present for more than 0.3 seconds.

The BCM stores DTC B2578 in memory.

1. A current DTC B2578 will clear if the BCM no longer detects a short to battery positive voltage in the autolamp relay control circuit, after the ignition is cycled.
2. A history DTC B2578 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.
3. The BCM receives a clear code command from the scan tool.

1. If the DTC B2578 is a history DTC, the fault may be intermittent. Refer to «TESTING FOR INTERMITTENT AND POOR CONNECTIONS»(/buick/century/vi-1997-2005/remont/body-electrical/#wiring-systems__testing-for-intermittent-and-poor-connections) in Wiring Systems.
2. The following conditions may cause an intermittent malfunction to occur: An intermittent short to battery in the automatic autolamp relay coil control circuit. The automatic autolamp relay coil is intermittently shorted to battery. The BCM is intermittently shorted to battery.

The numbers below refer to the step numbers on the diagnostic table.

1. 2. Listen for an audible click when the autolamp relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
2. 3. Verifies that the BCM is providing ground to the autolamp relay.
3. 4. Test for a short to battery position voltage in the control circuit of the automatic autolamp relay.

Scheme 81

The Body Control Module (BCM) controls the park lamp relay through the park lamp relay control circuit. The BCM grounds the park lamp relay control circuit energizing the park lamp relay.

The BCM must not be commanding the park lamp relay to energize.

1. The BCM detects a short to ground or open in the park lamp relay control circuit when it is not trying to energize the Park Lamp relay.
2. The condition above must be present for more than 0.3 seconds.

The BCM stores DTC B2587 in memory.

1. A current DTC B2587 will clear if the short to ground or open in the park lamp relay control circuit is no longer detected by the BCM.
2. A history DTC B2587 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.
3. The BCM receives a clear code command from the scan tool.

1. If the DTC B2587 is a history DTC, the fault may be intermittent. Refer to «TESTING FOR INTERMITTENT AND POOR CONNECTIONS»(/buick/century/vi-1997-2005/remont/body-electrical/#wiring-systems__testing-for-intermittent-and-poor-connections) in Wiring Systems.
2. The following conditions may cause an intermittent malfunction to occur: An intermittent short to ground or open in the park lamp relay control circuit. The park lamp relay coil is intermittently shorted to ground or open. The BCM is intermittently shorted to ground or open.

The numbers below refer to the step numbers on the diagnostic table.

1. 2. Listen for an audible click when the park lamp relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
2. 4. Tests for voltage at the coil side feed of the park lamp relay. The LP Park fuse supplies power to the coil side feed of the park lamp relay.
3. 5. Verifies that the BCM is providing ground to the park lamp relay.
4. 6. Tests if ground is constantly being applied to the park lamp relay.

Scheme 82

Scheme 83

The Body Control Module (BCM) controls the park lamp relay through the park lamp relay control circuit. The BCM grounds the park lamp relay control circuit which energizes the park lamp relay.

The BCM must be commanding the park lamp relay to energize.

1. The BCM detects a short to battery in the park lamp relay control circuit when it is trying to energize the park lamp relay.
2. The condition above must be present for more than 0.3 seconds.

The BCM stores DTC B2588 in memory.

1. A short to battery in the park lamp relay control circuit is no longer detected by the BCM when the park lamp relay is commanded to energize. After the fault is removed the ignition must be cycled to clear the code.
2. A history DTC B2588 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.
3. The BCM receives a clear code command from the scan tool.

1. If the DTC B2588 is a history DTC, the fault may be intermittent. Refer to «TESTING FOR INTERMITTENT AND POOR CONNECTIONS»(/buick/century/vi-1997-2005/remont/body-electrical/#wiring-systems__testing-for-intermittent-and-poor-connections) in Wiring Systems.
2. The following conditions may cause an intermittent malfunction to occur: An intermittent short to battery positive voltage in the park lamp relay coil control circuit. The park lamp relay coil is shorted to battery positive voltage. The BCM is shorted to battery positive voltage.

The numbers below refer to the step numbers on the diagnostic table.

1. 2. Listen for an audible click when the park lamp relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
2. 3. Verifies that the BCM is providing ground to the park lamp relay. Indicating a short to battery positive voltage internal to the park lamp relay.
3. 4. Test for a short to battery positive voltage in the control circuit of the park lamp relay.

Scheme 84

The Body Control Module (BCM) illuminates LF turn signal lamp during Daytime Running Lamps (DRL) operation in the day mode. The BCM applies steady power to the LF turn signal lamp which illuminates the LF turn lamp in a non flashing mode.

The BCM must be commanding the LF turn signal lamp on.

1. The BCM detects a short to battery positive voltage in the LF turn signal lamp supply voltage circuit or the LF turn signal switch signal circuit.
2. The condition above must be present for more than 20 seconds.

The BCM stores DTC B2603 in memory.

1. A current DTC B2603 will clear if the BCM no longer detects a short to battery positive voltage in LF turn signal lamp supply voltage circuit or the LF turn signal switch signal circuit.
2. A history DTC B2603 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.
3. The BCM receives a clear code command from the scan tool.

1. If the DTC B2603 is a history DTC, the fault may be intermittent. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS in Wiring Systems.
2. The following conditions may cause an intermittent malfunction to occur: An intermittent short to battery in the LF turn signal lamp supply voltage circuit or the LF turn signal switch signal circuit The BCM is intermittently shorted to battery.

The numbers below refer to the step numbers on the diagnostic table.

1. 3. Tests for battery positive voltage at the turn signal lamp.
2. 4. Test the turn signal supply voltage circuit for a short to battery positive voltage.
3. 5. Test the turn signal switch signal circuit for a short to battery positive voltage.

Scheme 85

The Body Control Module (BCM) illuminates RF turn signal lamp during Daytime Running Lamps (DRL) operation in the day mode. The BCM applies steady power to the RF turn signal lamp which illuminates the RF turn signal lamp in a non flashing mode.

The BCM must be commanding the RF turn signal lamp on.

1. The BCM detects a short to battery positive voltage in the RF turn signal lamp supply voltage circuit or the RF turn signal switch signal circuit.
2. The condition above must be present for more than 20 seconds.

The BCM stores DTC B2608 in memory.

1. A current DTC B2608 will clear if the BCM no longer detects a short to battery positive voltage in RF turn signal lamp supply voltage circuit.
2. A history DTC B2608 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.
3. The BCM receives a clear code command from the scan tool.

1. If the DTC B2608 is a history DTC, the fault may be intermittent. Refer to «TESTING FOR INTERMITTENT AND POOR CONNECTIONS»(/buick/century/vi-1997-2005/remont/body-electrical/#wiring-systems__testing-for-intermittent-and-poor-connections) in Wiring Systems.
2. The following conditions may cause an intermittent malfunction to occur: An intermittent short to battery positive voltage in the RF turn signal lamp supply voltage circuit or the RF turn signal switch signal circuit The BCM is intermittently shorted to battery.

The numbers below refer to the step numbers on the diagnostic table.

1. 3. Tests for voltage at the turn signal lamp.
2. 4. Test the turn signal supply voltage circuit for a short to battery positive voltage.
3. 5. Test the turn signal switch signal circuit for a short to battery positive voltage.

Scheme 86

The BCM controls the ground for the courtesy lamps through the courtesy lamp low control circuit. The BCM applies voltage to the courtesy lamps through the courtesy lamps supply voltage circuit. Ground for the courtesy lamps is applied from G201 to the BCM.

The BCM must be commanding the theater dimming feature OFF.

1. The BCM detects that the output for the courtesy lamp low control circuit is low when it is expected to be high.
2. The condition above must be present for more than 0.3 seconds.

The BCM stores DTC B2617 in memory.

1. A current DTC 2617 will clear if the short to ground or open in the courtesy lamp low control circuit is no longer detected by the BCM.
2. A history DTC B2617 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present nor any other malfunction in the BCM is detected.
3. The BCM receives a clear code command from the scan tool.

1. If the DTC B2617 is a history DTC, the fault maybe intermittent. Refer to «TESTING FOR INTERMITTENT AND POOR CONNECTIONS»(/buick/century/vi-1997-2005/remont/body-electrical/#wiring-systems__testing-for-intermittent-and-poor-connections) in Wiring Systems.
2. The following conditions may cause an intermittent malfunction to occur: An intermittent short to ground or open in the courtesy lamp low control circuit An intermittent open in the courtesy lamp supply voltage circuit The BCM is intermittently shorted to ground or open

The numbers below refer to the step numbers on the diagnostic table.

1. 2. Watch for the courtesy lamps to illuminate. Command both the ON and OFF states. Repeat the commands as necessary.
2. 4. Tests for battery positive voltage at the courtesy lamps.

Scheme 87

The BCM controls the ground for the courtesy lamps through the courtesy lamp low control circuit. The BCM applies voltage to the courtesy lamps through the courtesy lamps supply voltage circuit. Ground for the courtesy lamps is applied from G201 to the BCM.

The BCM must command the courtesy lamp low control circuit on.

1. The BCM detects a high when the output should be low in the courtesy lamp low control circuit.
2. The condition above must be present for more than 0.3 seconds.

The BCM stores DTC B2618 in memory.

1. A current DTC B2618 will clear if the short to battery positive voltage in the courtesy lamp low control circuit is no longer detected by the BCM.
2. A history DTC B2618 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present and no other BCM faults are detected.
3. The BCM receives a clear code command from the scan tool.

1. If the DTC B2618 is a history DTC, the fault may be intermittent. Refer to «TESTING FOR INTERMITTENT AND POOR CONNECTIONS»(/buick/century/vi-1997-2005/remont/body-electrical/#wiring-systems__testing-for-intermittent-and-poor-connections) in Wiring Systems.
2. The following conditions may cause an intermittent malfunction to occur: An intermittent short to battery positive voltage in the courtesy lamp low control circuit. The BCM is intermittently shorted to battery.

The numbers below refer to the step numbers on the diagnostic table.

1. 2. Watch for the courtesy lamps to illuminate. Command both the ON and OFF states. Repeat the commands as necessary.
2. 3. Tests for short to battery positive voltage in the courtesy lamp low control circuit.

Scheme 88

The Body Control Module (BCM) uses the ambient light sensor signal to control the automatic autolamp control system and the Daytime Running Lamps (DRL). The ambient light sensor is connected directly to the BCM through the DRL ambient light sensor signal circuit and the DRL ambient light low reference circuit.

The DRL feature or the automatic autolamp control feature must be enabled.

1. The BCM detects a short to ground in the DRL ambient light sensor signal circuit.
2. The ambient light sensor is internally shorted.
3. The condition above must be present for more than 0.3 seconds.

1. The BCM stores DTC B2647 in memory.
2. The DRL will default to night mode and the headlamps, park lamps, tail lamps and side marker lamps will illuminate.

1. The BCM no longer detects a short to ground in the DRL ambient light sensor signal circuit.
2. A history DTC B2647 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.
3. The BCM receives a clear code command from the scan tool.

1. If the DTC B2647 is a history DTC, the fault may be intermittent. Refer to «TESTING FOR INTERMITTENT AND POOR CONNECTIONS»(/buick/century/vi-1997-2005/remont/body-electrical/#wiring-systems__testing-for-intermittent-and-poor-connections) in Wiring Systems.
2. The following conditions may cause an intermittent malfunction to occur: An intermittent short to ground in the DRL ambient light sensor signal circuit The ambient light sensor is intermittently shorted. The BCM is intermittently shorted to ground.

The numbers below refer to the step numbers on the diagnostic table.

1. 3. Tests for the proper operation of the circuit in the high voltage range.
2. 4. Tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to battery positive voltage.

Scheme 89

Scheme 90

The Body Control Module (BCM) uses the ambient light sensor signal to control the automatic autolamp control system and the Daytime Running Lamps (DRL). The ambient light sensor is connected directly to the BCM through the DRL ambient light sensor signal circuit and the DRL ambient light sensor low reference circuit.

The DRL feature of the automatic autolamp control feature must be enabled.

1. The BCM detects that the DRL ambient light sensor signal circuit is greater than 4 volts or is open when it is trying to enable the automatic autolamp control feature.
2. The DRL ambient light sensor signal circuit is open or shorted to battery positive voltage.
3. The DRL ambient light sensor low reference circuit is open or shorted to battery positive voltage.
4. The ambient light sensor is open internally.
5. The condition above must be present for more than 0.3 seconds.

1. The BCM stores DTC B2648 in memory.
2. Headlamps, park lamps, tail lamps and side marker lamps illuminate.

1. The BCM no longer detects the fault in the ambient light sensor circuit.
2. A history DTC B2648 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.
3. The BCM receives a clear code command from the scan tool.

1. If the DTC B2648 is a history DTC, the fault may be intermittent. Refer to «TESTING FOR INTERMITTENT AND POOR CONNECTIONS»(/buick/century/vi-1997-2005/remont/body-electrical/#wiring-systems__testing-for-intermittent-and-poor-connections) in Wiring Systems.
2. The following conditions may cause an intermittent malfunction to occur: An intermittent open or short to battery positive voltage in the DRL ambient light sensor signal circuit. The ambient light sensor is intermittently open. The BCM is intermittently open or shorted to battery positive voltage.

The numbers below refer to the step numbers on the diagnostic table.

1. 3. Tests for the proper operation of the circuit in the high voltage range.
2. 4. Tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to battery positive voltage.

Scheme 91

Scheme 92

1. Perform the «DIAGNOSTIC SYSTEM CHECK - LIGHTING SYSTEMS»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems) No DTCs are set. The control module(s) can communicate via the serial data link.
2. Review the system operation in order to familiarize yourself with the system functions. Refer to «EXTERIOR LIGHTING SYSTEMS DESCRIPTION AND OPERATION»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems) or «INTERIOR LIGHTING SYSTEMS DESCRIPTION AND OPERATION»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems) .

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the Lighting System. Refer to «CHECKING AFTERMARKET ACCESSORIES»(/buick/century/vi-1997-2005/remont/body-electrical/#wiring-systems__checking-aftermarket-accessories) in Wiring Systems.
2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS in Wiring Systems.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

1. «Backup Lamps Always On»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
2. «Backup Lamps Inoperative»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
3. «Cornering Lamps Inoperative»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
4. «Cornering Lamps Always On»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
5. «Courtesy Lamps Always On»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
6. «Courtesy Lamps Inoperative»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
7. «Daytime Running Lamps (DRL) Inoperative»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
8. «Fog Lamp Indicator Inoperative»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
9. «Fog Lamps Always On»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
10. «Fog Lamps Inoperative»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
11. «Hazard Lamps Inoperative»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
12. «Headlamps Always On - Low Or High Beam»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
13. «Headlamps Inoperative - High Beams»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
14. «Headlamps Inoperative - Low Beams»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
15. «Headlamps Inoperative - Low and High Beams»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
16. «Headlamps Inoperative - Flash to Pass»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
17. «High Beam Indicator Inoperative»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
18. «Illuminated Entry Lamps Inoperative»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
19. «Instrument Panel (I/P) Compartment Lamp Inoperative»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
20. «Instrument Panel (I/P) Compartment Lamp Always On»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
21. «Interior Backlighting Does Not Dim»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
22. «Interior Backlighting Inoperative»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
23. «Park Lamps Always On»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
24. «Park Lamps Inoperative»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
25. «Reading Lamp(s) Always On»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
26. «Reading Lamp(s) Inoperative»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
27. «Rear Compartment Lamp(s) Always On»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
28. «Rear Compartment Lamp(s) Inoperative»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
29. «Rearview Mirror Lamp(s) Inoperative - Inside»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
30. «Stop Lamps Always On»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
31. «Stop Lamps Inoperative»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
32. «Turn Signal Lamps and/or Indicators Always On or Flashing»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
33. «Turn Signal Lamps and/or Indicators Inoperative»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
34. «Vanity Mirror Lamp(s) Always On»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)
35. «Vanity Mirror Lamp(s) Inoperative»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems)

Scheme 93

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Scheme 109

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Scheme 118

Scheme 119

Scheme 120

Scheme 121

Scheme 122

Scheme 123

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Scheme 125

Scheme 126

Scheme 127

Scheme 128

Scheme 129

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Scheme 141

Scheme 142

Scheme 143

Scheme 144

Scheme 145

Scheme 146

Scheme 147

Scheme 148

Scheme 149

Scheme 150

Scheme 151

Scheme 152

Scheme 153

Scheme 154

1. With the brake pedal in the fully released position, ensure that the stop lamp plunger is fully depressed against the brake pedal shanks.
2. Fully insert the stop lamp switch and the cruise control switch, if equipped, into the brake pedal bracket.
3. Push the brake pedal forward in order to set the brake push rod into the booster. NOTE: Proper stoplamp switch adjustment is essential. Improper stoplamp switch adjustment may cause brake drag, heat buildup and excessive brake lining wear.
4. Pull the brake pedal to the rear, against the internal stop. This adjusts both the stop lamp switch and the cruise control switch.
5. Inspect the stop lamp switch for proper adjustment.

Scheme 155

1. Remove the left side of the instrument panel (I/P) insulator.
2. Disconnect the electrical connector from the stop lamp switch.
3. Remove the stop lamp switch (2) from the brake pedal bracket.

Scheme 156

1. Install the stop lamp switch (2) to the brake pedal bracket.
2. Connect the electrical connector to the stop lamp switch.
3. Install the left side of the I/P insulator.
4. Adjust the stop lamp switch. Refer to «STOP LAMP SWITCH ADJUSTMENT»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems) .

Scheme 157

Scheme 158

1. Pull the rearward edge of the access opening cover outboard on the left side of the instrument panel (I/P) to release the retainers. Use a plastic flat-bladed tool as an aid if necessary.
2. Release the forward edge of the access opening cover from behind the hinge pillar and remove the cover.
3. Remove the autolamp switch screws.
4. Carefully pull the autolamp switch outboard away from the I/P to access the electrical connector.
5. Disconnect the electrical connector from the autolamp switch.

Scheme 159

Scheme 160

1. Connect the electrical connector to the autolamp switch.
2. Align the autolamp switch tabs to the I/P and press the switch into position. NOTE: Refer to «FASTENER NOTICE»(/buick/century/vi-1997-2005/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
3. Install the autolamp switch screws. Tighten Tighten the screws to 1.8 N.m (16 lb in).
4. Align and insert the forward edge of the left I/P access opening cover behind the hinge pillar.
5. Align the access opening cover retainers to the slots on the I/P trim pad and press firmly to secure.

Scheme 161

1. Remove the left instrument panel insulator. Refer to CLOSEOUT/INSULATOR PANEL REPLACEMENT - LEFT in Instrument Panel, Gages and Console.
2. Remove the steering column filler. Refer to STEERING COLUMN FILLER REPLACEMENT in Instrument Panel, Gages and Console.
3. Disconnect the electrical connector from the fog lamp switch.
4. Press the retaining tabs and remove the fog lamp switch from the steering column filler.

Scheme 162

1. Position the fog lamp switch to the steering column filler and press into place to secure.
2. Connect the electrical connector to the fog lamp switch.
3. Install the steering column filler. Refer to STEERING COLUMN FILLER REPLACEMENT in Instrument Panel, Gages and Console.
4. Install the left instrument panel insulator. Refer to CLOSEOUT/INSULATOR PANEL REPLACEMENT - LEFT in Instrument Panel, Gages and Console.

Scheme 163

1. Remove the garnish molding from the right windshield pillar. Refer to GARNISH MOLDING REPLACEMENT - WINDSHIELD PILLAR in Interior Trim.
2. Starting at the right side, carefully lift upwards on the instrument panel (IP) upper trim panel in order to release the retainers from the IP upper trim pad. Work towards the left in order to access the daytime running lamp (DRL) ambient light sensor (1).
3. Remove the DRL ambient light sensor from the IP upper trim panel by twisting the sensor 1/4 turn counterclockwise.
4. Remove the DRL ambient light sensor from the DRL ambient light sensor connector.

Scheme 164

1. Install the daytime running lamp (DRL) ambient light sensor (1) to the DRL ambient light sensor connector.
2. Position the DRL ambient light sensor to the opening in the instrument panel (IP) upper trim panel. Twist the DRL ambient light sensor 1/4 turn clockwise.
3. Verify that the DRL ambient light sensor wiring harness will not be pinched when the IP upper trim panel is installed. Working from left to right, press down on the IP upper trim panel in order to engage the retainers to the IP upper trim pad.
4. Install the garnish molding to the right windshield pillar. Refer to GARNISH MOLDING REPLACEMENT - WINDSHIELD PILLAR in Interior Trim.

Scheme 165

1. Remove the left instrument panel (I/P) insulator. Refer to CLOSEOUT/INSULATOR PANEL REPLACEMENT - LEFT in Instrument Panel, Gages and Console.
2. Remove the steering column filler panel. Refer to STEERING COLUMN FILLER REPLACEMENT in Instrument Panel, Gages, and Console.
3. Remove the I/P driver knee bolster bracket. Refer to KNEE BOLSTER REPLACEMENT in Instrument Panel, Gages, and Console.
4. Grasp the hazard and turn signal flasher and slide the flasher to the right to release the flasher tabs from the slots on the BCM bracket.
5. Disconnect the electrical connector from the flasher.

Scheme 166

1. Connect the electrical connector to the hazard and turn signal flasher.
2. Position the flasher to the BCM bracket, then slide the flasher to the left to secure the flasher tabs into the retaining slots on the bracket.
3. Install the I/P driver knee bolster bracket. Refer to KNEE BOLSTER REPLACEMENT in Instrument Panel, Gages, and Console.
4. Install the steering column filler panel. Refer to STEERING COLUMN FILLER REPLACEMENT in Instrument Panel, Gages, and Console.
5. Install the left I/P insulator. Refer to CLOSEOUT/INSULATOR PANEL REPLACEMENT - LEFT in Instrument Panel, Gages, and Console.

Scheme 167

1. Open the ashtray.
2. Rotate the socket clockwise. Pull the socket from the housing.
3. Pull the bulb from the socket.

Scheme 168

1. Install the bulb to the socket.
2. Press the socket into the housing. Rotate the socket counterclockwise.
3. Close the ashtray.

Scheme 169

1. Remove the front console and reposition the console slightly rearward. Refer to CONSOLE REPLACEMENT - FRONT FLOOR (D06) in Instrument Panel, Gages and Console.
2. Disconnect the electrical connector (2) from the console compartment lamp switch.
3. Open the console compartment door.
4. Release the retaining tab on the underside of the switch, while sliding the switch rearward.
5. Lift to remove the switch from the top of the console compartment.
6. Remove the console compartment lamp housing on top of the console compartment by pressing the housing towards one side and lifting to release.
7. Slide the lamp housing toward the opposite side to release the remaining tab and lift the housing away from the console compartment.
8. Rotate the lamp socket counterclockwise to release from the housing.
9. Remove the bulb (3) from the socket.

Scheme 170

1. Install the bulb (3) to the socket.
2. Install the lamp socket to the lamp housing, then rotate clockwise to secure.
3. Insert one side tab of the lamp housing into position on the top of the console compartment.
4. Press the lamp housing toward the installed side and lower the opposite side into position, the release. Check to be sure that the lamp is secure.
5. Align the console compartment lamp switch to the top of the console compartment.
6. Install the switch into place to secure.
7. Connect the electrical connector (2) to the console compartment lamp switch.
8. Position and install the front floor console. Refer to CONSOLE REPLACEMENT - FRONT FLOOR (D06) in Instrument Panel, Gages and Console.

Scheme 171

1. Remove the front floor console and reposition the console slightly rearward. Refer to CONSOLE REPLACEMENT - FRONT FLOOR (D06) in Instrument Panel, Gages and Console.
2. Disconnect the electrical connector (2) from the console compartment lamp switch.
3. Open the console compartment door.
4. Release the retaining tab on the underside of the switch, while sliding the switch rearward.
5. Lift to remove the switch from the top of the console compartment.

Scheme 172

1. Align the console compartment lamp switch to the top of the console compartment.
2. Press the switch into place to secure.
3. Connect the electrical connector (2) to the console compartment lamp switch.
4. Position and install the front floor console. Refer to CONSOLE REPLACEMENT - FRONT FLOOR (D06) in Instrument Panel, Gages and Console.

Scheme 173

Scheme 174

Scheme 175

Scheme 176

Scheme 177

1. Remove the front door trim panel enough to access the courtesy lamp. Refer to TRIM PANEL REPLACEMENT - SIDE FRONT DOOR in Doors.
2. Disconnect the electrical connector from the courtesy lamp.
3. Release the courtesy lamp by depressing the forward retainer.
4. Remove the courtesy lamp out of the front door trim panel, by pressing outward on the courtesy lamp and pulling out from the front of the door trim panel.
5. Rotate the lamp socket counterclockwise to release the socket from the lamp housing, then remove the socket.
6. Remove the bulb from the socket.

Scheme 178

Scheme 179

Scheme 180

Scheme 181

Scheme 182

Scheme 183

1. Install the bulb to the door courtesy lamp socket.
2. Install the lamp socket to the courtesy lamp housing, then rotate the socket clockwise.
3. Position the courtesy lamp to the front door trim panel.
4. Align the rear edge of the courtesy lamp retainer tab to the front door trim panel.
5. Install the courtesy lamp to the front door trim panel pressing the forward edge into place until the retainer is fully seated.
6. Connect the electrical connector from the courtesy lamp.
7. Install the front door trim panel. Refer to TRIM PANEL REPLACEMENT - SIDE FRONT DOOR in Doors.

Scheme 184

1. Lower the appropriate instrument panel (I/P) insulator. Refer to CLOSEOUT/INSULATOR PANEL REPLACEMENT - RIGHT or to CLOSEOUT/INSULATOR PANEL REPLACEMENT - LEFT in Instrument Panel, Gages, and Console.
2. Rotate the courtesy lamp socket counterclockwise. Remove the socket from the insulator.
3. Pull the bulb from the socket.

Scheme 185

1. Install the bulb to the socket.
2. Install the courtesy lamp socket to the I/P insulator. Rotate the socket clockwise to secure.
3. Install the IP insulator. Refer to CLOSEOUT/INSULATOR PANEL REPLACEMENT - RIGHT or to CLOSEOUT/INSULATOR PANEL REPLACEMENT - LEFT in Instrument Panel, Gages, and Console.

Scheme 186

1. Open the instrument panel (I/P) compartment door.
2. Depress the retaining tabs on the top and bottom of the I/P compartment lamp switch.
3. Push the switch out of the opening.
4. Disconnect the electrical connector from the IP compartment lamp switch.
5. Remove the I/P compartment lamp switch.

Scheme 187

1. Connect the electrical connector to the I/P compartment lamp switch.
2. Position the I/P compartment lamp switch to the opening. Press the switch into the opening.
3. Close the I/P compartment door.

Scheme 188

1. Open the instrument panel (I/P) compartment door.
2. Depress the retaining tabs on the top and bottom of the I/P compartment lamp switch.
3. Push the switch out of the opening.
4. Pull the bulb from the switch.

Scheme 189

1. Install the bulb to the I/P compartment lamp switch.
2. Press the switch into the opening.
3. Close the I/P compartment door.

Scheme 190

Scheme 191

1. Use a small flat-bladed tool to disengage the edge of the lamp lens. Remove the lens from the rearview mirror.
2. Carefully remove the bulb from the socket.

Scheme 192

Scheme 193

1. Install the bulb to the socket.
2. Align the lamp lens to the rearview mirror. Press the lens into place.

Scheme 194

Scheme 195

1. Lower the sunshade and raise the mirror and lamp cover door.
2. Insert a small flat-bladed tool at the lower edge of the lamp lens towards the middle of the sunshade. Lift the lens enough to clear the plastic housing.
3. Remove the vanity mirror lamp lens from the sunshade.
4. Remove the bulb from the socket.

Scheme 196

Scheme 197

1. Install the bulb into the socket.
2. Position the vanity mirror lamp lens to the sunshade.
3. Align the lens tabs into the housing slots and insert the upper edge of the lens first.
4. Insert a small flat-bladed tool at the lower edge of the vanity mirror lamp lens then press up to fully install the lens.
5. Close the lamp cover door and raise the sunshade.

Scheme 198

1. Remove the front floor console trim plate. Refer to TRIM PLATE REPLACEMENT - CONSOLE FRONT in Instrument Panel, Gages and Console.
2. Grasp the floor shift control trim bezel and lift to release the retaining tabs.
3. Rotate the floor shift control indicator lamp socket counterclockwise to release from the trim bezel.
4. Remove the bulb from the socket.

Scheme 199

1. Install the bulb to the socket.
2. Install the floor shift control indicator lamp socket to the trim bezel, then rotate the socket clockwise to secure.
3. Install the floor shift control trim bezel into position and press into place to secure the retaining tabs.
4. Install the front floor console trim plate. Refer to TRIM PLATE REPLACEMENT - CONSOLE FRONT in Instrument Panel, Gages and Console.

Scheme 200

Scheme 201

1. Squeeze together the front and rear edges of the dome lamp housing to release the retainers along the sides of the housing. Pull the housing down and away from the dome lamp base plate.
2. Drill out the rivets from the lamp base plate.
3. Remove the bulb from the dome lamp socket.
4. Remove the dome lamp base plate from the roof.
5. Disconnect the electrical connector from the dome lamp base plate.

Scheme 202

Scheme 203

1. Connect the electrical connector to the dome lamp base plate.
2. Position the dome lamp base plate to the roof and install the new rivets to the base plate.
3. Install the bulb to the dome lamp socket.
4. Align the dome lamp housing to the base plate and press into place until fully seated.

Scheme 204

1. Squeeze together the front and rear edges of the dome lamp housing to release the retainers along the sides of the housing. Pull the housing down and away from the dome lamp base plate.
2. Remove the bulb from the dome lamp socket.

Scheme 205

1. Install the bulb to the dome lamp socket.
2. Align the dome lamp lens housing to the base plate and press into place until fully seated.

Scheme 206

Scheme 207

Scheme 208

Scheme 209

Scheme 210

1. Open the hood.
2. Apply light pressure to the autolamp lens to hold the autolamp in place while removing the retainers.
3. Lift up the autolamp retainers to release, then remove the retainers.
4. Remove the autolamp mounting tabs from the slots in the upper fascia support and the fender reinforcement.
5. Disconnect the electrical connector from the autolamp.
6. Remove the autolamp.
7. Remove the rubber access covers from behind the autolamp bulb/sockets to be replaced. CAUTION: Refer to Halogen Bulb Caution in Cautions and Notices.
8. Rotate the autolamp bulb/socket counterclockwise to release.
9. Remove the autolamp bulb/socket from the autolamp.
10. Disconnect the electrical connector from the autolamp bulb/socket.

Scheme 211

Scheme 212

Scheme 213

Scheme 214

Scheme 215

1. Connect the electrical connector to the autolamp bulb/socket.
2. Install the autolamp bulb/socket to the autolamp.
3. Rotate the autolamp bulb/socket clockwise until fully seated.
4. Install the rubber access covers to the autolamp.
5. Connect the electrical connector to the autolamp.
6. Position the autolamp mounting tabs to the slots in the upper fascia support and the fender reinforcement.
7. Apply light pressure to the autolamp lens to hold the autolamp in place while installing the retainers.
8. Align the autolamp retainers over the autolamp mounting tabs, then press the retainers down until fully seated.
9. Inspect the autolamp for proper fit.
10. Check the autolamp aim, if a new autolamp was installed, or if service or repairs in the front end area may have disturbed the autolamp mounting brackets. Refer to «HEADLAMP AIMING»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems) .
11. Close the hood.

Visual Aiming Procedure

Headlamp aim should be checked

Scheme 216

1. When a new autolamp capsule is installed
2. If service or repairs to the front end area have (or may have) disturbed the headlamps or their mounting
3. The area will consist of a level surface large enough to allow for a vehicle and an additional 7.62 m (25 ft) measured from face of lamps to the front of the aiming screen.
4. The screen will be 1.52 m (5 ft) high x 3.66 m (12 ft) wide with a matte white surface well shaded from extraneous light, and properly adjusted to the floor on which the vehicle stands. Provisions may be made for moving the screen so it can be aligned parallel with the vehicle.
5. The screen shall be provided with a fixed vertical centerline, two laterally adjustable vertical tapes, and one vertically adjustable horizontal tape.
6. If a regular commercial aiming screen is not available, the screen may consist of a vertical wall having a clear uninterrupted area approximately 1.83 m (6 ft) high and 3.66 m (12 ft) wide. The surface should be finished with a washable non-gloss white paint.
7. After the aiming screen has been set up in its permanent location, it is necessary to paint a reference line on the floor directly under the lens of the lamps to indicate the proper location of the headlamps when they are being aimed: Distance between headlamps (1) Center line of screen (2) Adjustable vertical pointer (3) Adjustable horizontal tape (4) Diagram of light screen (5) Vertical center line ahead of right autolamp pointer position (6) 7.62 m (25 ft) (7) Car axis (8) Adjustable vertical pointer Horizontal center line of lamps Vertical center line ahead of left autolamp

Prior to aiming the headlamps, the following Steps must be taken

Scheme 217

1. Remove any snow, ice or mud from the vehicle.
2. The vehicle must have a full tank of gas.
3. Stop all other work on the vehicle.
4. If any service has been performed on the vehicle, make sure that all of the components are back in their original place.
5. The vehicle must be on a level surface.
6. The vehicle left tires must be aligned with the reference line extending from the screen with the headlamps aligned with the reference line.
7. Do not load any cargo in the vehicle.
8. The vehicle must contain one person or 72.56 kg (160 lb) on the driver's seat.
9. Inflate the tires to the proper pressure.
10. Simulate the vehicle loads if the intended use of the vehicle is for hauling heavy loads or towing a trailer.
11. Rock the vehicle in order to stabilize the suspension.
12. Turn on the headlamps to low beam and observe the left and the top edges of the high intensity zone on the screen. The edges of the high intensity zone should fall within the specifications.

Scheme 218

Scheme 219

Scheme 220

1. Open the hood.
2. Measure from the floor to the center of the autolamp bulb. (Some headlamps have an aim dot marked on the autolamp lens).
3. At the screen, measure from the floor and place the horizontal tape at the measured distance.
4. Measure from the reference line on the floor to the left autolamp bulb centerline.
5. At the screen, measure from the reference line and place the vertical tape at the measured distance.
6. Measure from the reference line on the floor to the right autolamp bulb centerline.
7. At the screen, measure from the reference line and place the vertical tape at the measured distance. IMPORTANT: DO NOT cover the autolamp, this may cause excessive heat build up.
8. Turn on the low beam headlamps and block the light from projecting onto the screen from the passenger side autolamp.
9. Adjust the horizontal aim screw (1) and vertical aim screw (4) of the headlamps to the specifications required by the state and the local authorities, or as shown in step number 8.
10. Repeat the aiming procedure for the passenger side autolamp while blocking the light from projecting onto the screen from the driver side autolamp.
11. Turn the headlamps OFF.
12. Close the hood.

Scheme 221

Scheme 222

Scheme 223

1. Remove the front bumper fascia deflector. Refer to FRONT BUMPER FASCIA DEFLECTOR REPLACEMENT - SIDE in Bumpers.
2. Disconnect the electrical connector from the front fog lamp assembly.
3. Remove the fog lamp bulb/socket from the fog lamp by rotating counterclockwise.
4. Remove the front fog lamp nuts from the front bumper impact bar.
5. Remove the front fog lamp assembly from the vehicle.

Scheme 224

Scheme 225

Scheme 226

1. Position the front fog lamp assembly to the front bumper impact bar. NOTE: Refer to «FASTENER NOTICE»(/buick/century/vi-1997-2005/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
2. Install the front fog lamp nuts to the front bumper impact bar. Tighten Tighten the nuts to 10 N.m (89 lb in).
3. Install the fog lamp bulb/socket to the fog lamp by rotating clockwise.
4. Connect the electrical connector to the front fog lamp assembly.
5. Install the front bumper fascia deflector. Refer to FRONT BUMPER FASCIA DEFLECTOR REPLACEMENT - SIDE in Bumpers.
6. Check and adjust the front fog lamp aim as necessary. Refer to «FOG LAMP AIMING PROCEDURE»(/buick/century/vi-1997-2005/remont/exterior-lights/#lighting-systems__fog-lamp-aiming-procedure) .

Scheme 227

Scheme 228

1. Remove the front bumper fascia deflector. Refer to FRONT BUMPER FASCIA DEFLECTOR REPLACEMENT - SIDE in Bumpers.
2. Disconnect the electrical connector from the front fog lamp bulb/socket. CAUTION: Refer to Halogen Bulb Caution in Cautions and Notices.
3. Rotate the front fog lamp bulb/socket counterclockwise to release.
4. Remove the fog lamp bulb/socket from the front fog lamp assembly.

Scheme 229

Scheme 230

1. Install the fog lamp bulb/socket to the fog lamp rotating clockwise until fully seated. CAUTION: Refer to Halogen Bulb Caution in Cautions and Notices.
2. Connect the electrical connector to the front fog lamp bulb/socket.
3. Install the front bumper fascia deflector. Refer to FRONT BUMPER FASCIA DEFLECTOR REPLACEMENT - SIDE in Bumpers.

Fog Lamp Aiming Procedure

The front fog lamps must be aimed for proper illumination of the road. The front fog lamp aim should be checked when a new front fog lamp assembly is installed, or if service or repairs in the front end area may have disturbed the front fog lamp mounting.

Preparation Procedure

1. Completely assemble all of the components on the vehicle.
2. Place the vehicle on a level surface.
3. Stop all unnecessary operations or work that could affect the ride height of the vehicle.
4. Close the doors and verify that the luggage compartment is empty.
5. Stabilize the suspension by rocking the vehicle sideways.
6. Ensure that the fuel level is full.
7. Ensure that the tires are inflated to the proper pressure.
8. Ensure that the driver or a similar weight, approximately 75 kg (165 lbs) is in the vehicle driver seat.

Scheme 231

Scheme 232

1. Park the vehicle 7.6 m (25 ft) away from the target screen.
2. Measure from the center of the fog lamp to the ground line. Using this measurement, mark the horizontal centerline (2) of the fog lamp on the target screen directly in front of the vehicle.
3. Turn ON the fog lamps. The top of the fog lamp beam image (4) on the target screen should be 102 mm (4 in) below the center of the fog lamp lens height.
4. Reach under the rear lower edge of the front fascia to access the fog lamp vertical adjustment nut (1).
5. Adjust the fog lamp as required, using the adjusting nut (1) on the bottom of the fog lamp.
6. Turn OFF the fog lamps.

Scheme 233

Scheme 234

1. Open the rear compartment lid.
2. Rotate the high-mounted stop lamp socket counterclockwise. Pull the socket from the high-mounted stop lamp.
3. Remove the bulb from the socket.

Scheme 235

Scheme 236

1. Install the bulb to the socket.
2. Position the socket into the high-mounted stop lamp opening. Rotate the socket clockwise.
3. Close the rear compartment lid.

Scheme 237

1. Remove the rear compartment lid applique. Refer to COMPARTMENT LID APPLIQUE REPLACEMENT - REAR in Body Rear End.
2. Remove the backup lamp bulb/sockets from the applique by rotating counterclockwise.
3. Remove the backup lamp bulbs from the sockets, if required.

Scheme 238

1. Install the backup lamp bulbs to the sockets, if removed.
2. Install the backup lamp bulb/sockets to the applique by rotating clockwise until fully seated.
3. Install the rear compartment lid applique. Refer to COMPARTMENT LID APPLIQUE REPLACEMENT - REAR in Body Rear End.

Scheme 239

1. Remove the rear compartment lid applique. Refer to COMPARTMENT LID APPLIQUE REPLACEMENT - REAR in Body Rear End.
2. Rotate the license lamp sockets counterclockwise to release from the license lamps on the rear compartment lid applique.
3. Remove the license lamp bulbs from the sockets.

Scheme 240

1. Install the license lamp bulbs to the license lamp sockets.
2. Install the license lamp sockets to the license lamp on the lid applique, then rotate clockwise to secure.
3. Install the rear compartment lid applique. Refer to COMPARTMENT LID APPLIQUE REPLACEMENT - REAR in Body Rear End.

Scheme 241

Scheme 242

Scheme 243

1. Open the rear compartment.
2. Remove the rear compartment convenience net, if equipped, from the plastic wingnut retainers.
3. Remove the visible plastic wingnut retaining the tail lamp.
4. Pull back the corner of the rear compartment trim panel to access the remaining plastic wingnuts.
5. Apply light pressure to the tail lamp lens to retain the lamp in position during removal of the remaining plastic wingnut retainers.
6. Remove the remaining plastic wingnuts retaining the tail lamp.
7. Remove the tail lamp assembly from the rear body panel and support the tail lamp assembly.
8. Rotate the lamp sockets counterclockwise to remove them from the tail lamp housing.
9. Remove the tail lamp housing assembly.
10. Remove the tail lamp bulbs from the sockets, if required.

Scheme 244

Scheme 245

Scheme 246

1. Install the tail lamp bulbs to the sockets, if removed.
2. Install the tail lamp sockets to the tail lamp housing, rotating clockwise until fully seated.
3. Position the tail lamp assembly to the rear body panel.
4. Apply light pressure to the lens to retain the lamp in position during installation of the plastic wingnut retainers.
5. Install the tail lamp assembly plastic wingnut retainers.
6. Install the corner of the rear compartment trim panel into position.
7. Install the remaining tail lamp plastic wingnut retainer.
8. Install the rear compartment convenience net, if equipped, to the plastic wingnut retainers.
9. Close the rear compartment.

Scheme 247

Scheme 248

Scheme 249

Scheme 250

Scheme 251

1. Open the assist handle covers.
2. Remove the side rail lamp assist handle screws.
3. Remove the assist handle. IMPORTANT: Note the location of the side rail lamp assist handle plastic retainers.
4. Remove the side rail lamp base plate.
5. Disconnect the electrical connector from the side rail lamp.
6. Remove the side rail lamp socket from the base plate by sliding off.
7. Remove the bulb.

Scheme 252

Scheme 253

Scheme 254

Scheme 255

Scheme 256

1. Install the bulb.
2. Install the side rail lamp socket to the base plate by sliding on.
3. Connect the electrical connector to the side rail lamp.
4. Align the side rail lamp base plate to the plastic retainers.
5. Position the side rail lamp assist handle to the base plate and the plastic retainers. NOTE: Refer to «FASTENER NOTICE»(/buick/century/vi-1997-2005/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
6. Install the side rail lamp assist handle screws. Tighten Tighten the side rail lamp assist handle screws to 2 N.m (18 lb in).
7. Close the assist handle covers pressing into place until fully seated.

Scheme 257

1. Open the rear compartment lid.
2. Using a small flat-bladed tool, carefully release the rear compartment lamp retaining tabs and lower the lamp.
3. Remove the bulb from the lamp socket.

Scheme 258

1. Install the bulb to the rear compartment lamp socket.
2. Align the rear compartment lamp, then press into place to secure the lamp retaining tabs.
3. Close the rear compartment lid.

Exterior Lamps

The exterior lighting system includes the following components

1. Headlamps (high and low beam)
2. Front park/turn signal lamps
3. Front cornering lamps
4. Tail/rear turn signal lamps
5. Front sidemarker lamps
6. Rear sidemarker lamps
7. High-mounted stop lamps
8. Backup lamps
9. Rear license lamps

This system also includes all wiring controls and related hardware required for the operation of these lamps.

Headlamps

The headlamps may be turned on two different ways. First, when the driver places the autolamp switch in the ON position, for normal operation. Second, with the autolamp switch placed in the OFF position, during Daytime Running Lamp (DRL) operation in low light conditions.

The HDLP L and HDLP R fuse in the fuse block - underhood, supply battery positive voltage to both low beam lamps and high beam lamps at all times. The low beam and high beam circuits continue to the autolamp dimmer switch, the low beam or high beam circuit is then, depending on the position of the dimmer switch, connected to the autolamp switch. When the autolamp switch is placed in the ON position, it provides a ground path for the low beam or high beam lamps through G201. The autolamp switch also provides a input signal to the BCM in order to determine if the headlamps are ON.

During automatic autolamp operation in low light conditions the BCM will pull the automatic autolamp relay low, energizing it. When the autolamp relay energizes, it provides a ground path for the low beam or high beam lamps through G201, depending on the dimmer switch position.

Both the autolamp switch and the automatic autolamp relay can provide a ground for the headlamps for manual or automatic headlight operation. The headlights may be switched to high beam by pulling the dimmer switch handle toward the driver until the high beam dimmer switch is activated. When the dimmer switch is placed in the HIGH BEAM position, the indicator lamp and the high beam lamps are grounded and illuminate.

Flash to Pass

The flash to pass feature can be operated with the low beams OFF or ON. The high beams may be momentarily turned on or flashed with the dimmer switch handle. When the autolamp dimmer switch handle is pulled toward the driver, the flash-to-pass switch closes grounding the high beam circuit at G201, both high beams will remain on until the driver releases the switch handle. If the low beam headlamps were on during a flash-to-pass operation, they will remain on.

Daytime Running Lamps (DRL)

The front turn signal lamps are used as both Daytime Running Lamps and turn signals lamps. The Body Control Module (BCM) illuminates the front turn signals lamps in a non flashing mode for Daytime Running Lamps (DRL) operation. If the turn signal switch is activated during Daytime Running Lamp operation, the appropriate turn signal will flash.

The Daytime Running Lamps (DRL) are designed to be automatically illuminated when the ignition is ON and the outside (ambient) light level is high as in daytime conditions (day mode). The Daytime Running Lamps (DRL) will not operate if the ambient light levels are too low (night mode). Light levels are detected by the ambient light sensor, a light sensitive transistor that varies its voltage signal to the Body Control Module (BCM) in response to changes to the ambient light level. When the BCM receives a day mode signal from the ambient light sensor it will then illuminate the DRL lamps. The automatic headlamps and park lamps will not operate when the DRL lamps are on.

In the day mode, the ambient light sensor detects daylight and the BCM applies voltage to the LH and RH front turn signal lamps illuminating the lamps under the following conditions

1. The ignition switch is in the RUN position.
2. The headlamps are OFF.
3. The park brake is OFF (released).
4. The RH or LH turn signal is OFF.

Automatic Headlamps and Park Lamps

The automatic headlamps and park lamps are designed to automatically illuminate when the ignition is ON and the outside (ambient) light level is low as in night time conditions (night mode). Light levels are detected by the ambient light sensor, a light sensitive transistor that varies its voltage signal to the Body Control Module (BCM) in response to changes to the ambient light level. When the BCM receives a low light mode signal from the ambient light sensor it will then energize the park lamp and automatic autolamp relays illuminating the headlamps and park lamps. The DRL lamps will not operate when the automatic headlamps and park lamps are on.

In the low light mode, the ambient light sensor detects low light level, the BCM turns OFF the front turn signal lamps and grounds the park lamp relay and automatic autolamp relay control circuits, turning ON the headlamps and park lamps under the following conditions

1. The ignition switch is in the RUN position.
2. The headlamps are OFF.
3. The park brake is OFF (released).

If the engine stalls with the DRL in the low light mode, the BCM turns OFF the headlamps while the engine is being cranked. The park lamps will remain ON while the engine is being cranked.

Delayed Headlamp Control

The BCM has a delayed autolamp control feature that will leave the headlamps ON for a 90 seconds after the ignition switch is turned OFF, when the automatic autolamp are on and the autolamp switches is in the OFF position.

Park Brake Input

The BCM will not operate any headlamps or exterior lamps, if the park brake is applied before the ignition switch is turned to the RUN position. This allows the driver to start the vehicle and keep the headlamps OFF, as long as the park brake is applied. The BCM will activate the headlamps when the park brake is released with the ignition switch in the RUN position. This feature functions only when the park brake is applied before the ignition switch is turned to the RUN position. The headlamps will not turn OFF, if the park brake is applied after the ignition switch is turned to the RUN position.

Fog Lamps

The fog lamps are located in the bumper fascia beneath the autolamp assemblies. The front fog lamp switch is located below the autolamp switch on the left side of the Instrument Panel Cluster (IPC). Pressing the fog lamp switch button will turn the fog lamps ON, as long as the autolamp switch is NOT in the OFF position. When the fog lamps are ON, an indicator on the fog lamp switch will illuminate. Pressing the switch again will turn the fog lamps OFF.

The FOG LAMP relay in the fuse block - underhood controls the fog lamps. The switched side of the relay receives battery voltage at all times from the FOG LP Fuse. The coil side feed circuit of the fog lamp relay receives voltage from the HDLP fuses via an inactive high beam autolamp. The voltage will be pulled low with the high beams ON disabling the fog lamps. The BCM will provide an enable signal to the fog lamp switch when the ignition is ON and the autolamp switch is in PARK or HEAD position. With the fog lamp enable circuit active and the fog lamp switch is pressed, a ground is applied to the fog lamp relay control circuit. This energizes the relay, closing the switched contact and applying battery voltage to the fog lamps. The fog lamps receive a constant ground.

Turn Signal Lamps

The front turn signal lamps are made up of the front park/turn signal lamps and rear turn signal lamps. The front turn signal lamps flash with the rear turn signal lamps when a turn is initiated using the turn signal/multifunction lever. The turn signals will operate only with the ignition switch in the RUN position and will not operate during hazard flasher operation.

When the ignition is turned to the RUN position, battery voltage is supplied to the TURN SIGNAL Fuse. Battery voltage is then applied through the turn signal fuse circuit to the turn signal switch. When the turn signal switch is placed in the LH or RH position, voltage is supplied to the hazard lamp/turn signal lamp flasher. The hazard lamp/turn signal lamp flasher supplies a turn signal flasher signal to the turn signal switch. With the turn signal switch in the LH or RH position the corresponding turn signal indicator, rear turn signal, and front turn signal receive the turn signal switch signal and will flash. The front turn signals receive the turn signal switch signal from the turn signal switch via the BCM. The turn lamps are permanently grounded.

Hazard Lamps

The hazard warning switch is part of the turn signal switch. The turn signal switch receives battery voltage at all times through the HAZARD SWITCH Fuse. When the hazard switch is placed in the HAZARD position, battery voltage is applied to the hazard lamp/turn signal lamp flasher. The hazard lamp/turn signal lamp flasher sends a turn signal flasher signal to the turn signal switch. The turn signal switch provides all of the turn lamps and turn indicators with the turn signal flasher signal, simultaneously flashing them on and off.

Cornering Lamps

The front cornering lamps are located outboard of the low-beam autolamp bulb in each of the autolamp assemblies. The cornering lamps operate when a turn is initiated using the turn signal/multifunction lever. The cornering lamps will operate only with the ignition switch in the RUN position and will not operate during hazard flasher operation.

The TURN SIGNAL CORN LPS fuse supplies voltage to the turn signal switch when the ignition is in RUN. When the turn signal switch is placed in the LH or RH position the corresponding cornering lamp will receive voltage and illuminate. The cornering lamps are permanently grounded.

Park, Tail, Sidemarker, and Rear License Lamps

The front park lamps are made up of the front park/turn signal lamps and the front sidemarker lamps. The rear park lamps are made up of the rear tail/turn signal lamps, rear park lamps, rear sidemarker lamps, and rear license lamps.

The autolamp switch is used to operate all the park lamps and rear license lamps. The autolamp switch is located on the left side of the Instrument Panel Cluster (IPC). Pulling the knob of the autolamp switch out to the middle position will turn ON the park lamps. The park lamps can also be illuminated by the BCM during automatic autolamp operation in low light mode.

When the autolamp switch placed in the PARK position battery voltage is supplied through the autolamp switch to both the TAIL LAMP, LIC LAMPS fuse and the FRONT PARK fuse. Battery voltage is then applied through the TAIL LAMP LIC LAMPS fuse and the FRONT PARK fuse to the front and rear park lamps and the rear license lamps illuminating the lamps. The park lamps and rear license lamps receive ground at all times.

The park lamps can also be controlled by the park lamp relay during automatic autolamp operation in low light mode. Both the coil and the switched sides of the park lamp relay receive battery voltage at all times. When the BCM is in automatic autolamp operation, low light mode, the BCM then applies a ground through the park lamp relay coil control circuit to the park lamp relay. This energizes the relay closing the switch contact and applies battery voltage to both the TAIL LAMP, LIC LAMPS fuse and the FRONT PARK LAMP fuse. Battery voltage is then applied through the TAIL LAMP LIC LAMPS fuse and the FRONT PARK fuse to the front and rear park lamps and the rear license lamps illuminating the lamps. The park lamps and rear license lamps receive ground at all times.

Stop Lamps

The stop lamps consist of the center high mounted stop lamps and the LH and RH rear stop/turn lamps. The LH and RH rear stop/turn lamps are single-filament bulbs that are used as stop lamps and turn signal lamps.

The stop lamp switch receives battery voltage at all times through the STOP LAMPS fuse. When the brake pedal is pressed, the stoplamp switch closes and battery voltage is applied to the center high mounted stop lamps through the stop lamp switch signal circuit. The stop lamp switch signal circuit also sends battery voltage to the turn signal switch. The turn signal switch applies voltage to the rear stop/turn lamps through the turn signal lamp signal circuit, using the stop/turn signal lamps as stop lamps. The center high mounted stop lamp and the stop/turn signal lamps are permanently grounded.

Backup Lamps

The backup lamps are located in the rear compartment lid applique. The backup lamps operate when the ignition switch is in the RUN position and the transaxle range selector lever is in REVERSE.

The R/CMPT REL fuse supplies battery voltage at all the times to the coil side and the switched side of the backup relay. When the vehicle is placed in REVERSE, a class 2 signal is sent to the BCM. The BCM then applies a ground through the backup lamp relay coil control circuit to the backup lamps relay. This energizes the relay and allows battery positive voltage to be applied to the backup lamps turning them on. The backup lamps receive a constant ground signal

High Beam

The high beam indicator is hard wired to the autolamp switch. The high beam indicator illuminates when the autolamp switch is in the high position (signal circuit is low).

Turn Signals

The left and right turn signal indicators are hard wired to the turn signal switch and the hazard switch. The turn signal indicator illuminates when the turn signal lamps supply voltage circuit is active. The body control module (BCM) is also hard wired to the turn signal switch. If the BCM determines that the turn signal flasher signal circuit is active for more than 1.2 km (0.75 mi), the BCM activates an audible warning.

Driver Controls and Modules

The Body Control Module (BCM) module processes the inputs and the controls. The ambient light sensor supplies the BCM with a signal for daytime conditions or for low light conditions

1. The Body Control Module (BCM)
2. The ambient light sensor
3. The Instrument Panel Cluster (IPC)

Driver controls include the following components

1. The fog lamp switch
2. The door lock switches
3. The autolamp dimmer switch
4. The autolamp switch
5. The park/neutral position switch
6. The park brake indicator switch
7. The stop lamp switch
8. The turn signal switch

Interior Lighting

The interior lighting consist of lamps that may not be dimmed (Interior Lamps) and lamps that may be dimmed (Interior Lamps Dimming).

Interior Lamps

The first group of lamps are the interior lamps these includes the lamps that may not be dimmed manually

1. The dome lamp
2. The IP compartment lamp
3. The IP courtesy lamps
4. The inside rear view mirror lamps
5. The rear compartment lamp
6. The roof rail courtesy lamps
7. The sunshade mirror lamps
8. The underhood compartment lamp

Interior Lamps Features

The interior lamps system features the following functions

1. An illuminated entry feature that illuminates the courtesy lamps when entering the vehicle or activating the remote keyless entry system.
2. An illuminated exit feature that illuminates the courtesy lamps when the ignition key has been removed from the ignition.
3. An inadvertent power feature that supplies voltage to all interior lamps after the ignition is turned OFF. The inadvertent power feature will deactivate all interior lamps after 20 minutes to prevent battery rundown.
4. A theatre dimming feature that will slowly dim the interior lamps from full brightness to off.
5. An IP dimmer switch that illuminates the courtesy lamps.
6. Individual switches for control of each interior lamp that is not illuminate with the interior lamp switch.

Courtesy/Illuminated Entry Lamps

When the Body Control Module (BCM) is in an active state (awake) it energizes the courtesy lamps supply voltage circuit. The courtesy lamps supply voltage circuit supplies voltage to all of the interior lamps, including the illuminated entry lamps (courtesy lamps). The illuminated entry lamps are turned on when they receive a ground from the courtesy lamp low control circuit of the BCM. When the ignition is in the LOCK position the BCM will ground the courtesy lamp low control circuit under the following conditions

1. The door jamb input transitions to an active state (opening a door).
2. The use of the remote keyless entry (RKE) to unlock the side doors.

When the courtesy lamps supply voltage circuit and the courtesy lamp low control circuit are active the courtesy/illuminated entry lamps will illuminate. The courtesy lamps/illuminated entry lamps include the following interior lamps

1. The dome lamp
2. The roof rail courtesy lamps
3. The I/P courtesy lamps
4. The inside rear view mirror

When the driver uses the remote function actuator transmitter to unlock the doors, the BCM will illuminate the courtesy lamps for approximately 40 seconds, unless another BCM function causes the lamps to remain active. If the ignition switch is turned to either the RUN or START position the courtesy lamps will turn off immediately.

When the door latch switch signal circuit is active with the ignition in the OFF position the BCM will illuminate the courtesy lamps. The courtesy lamps will remain illuminated for approximately 25 seconds, after the door latch switch signal circuit becomes inactive, unless another BCM function causes the lamps to remain active. If the ignition switch is turned to either the RUN or START position the courtesy lamps will turn off immediately.

Courtesy/Illuminated Exit

The illuminated exit feature will activate the courtesy lamps when the key IN input of the BCM transitions from an active state to an inactive state (removing the ignition key). When the key is removed from the ignition, the key IN input to the BCM becomes inactive. The BCM will illuminate the courtesy lamps for approximately 25 seconds, unless another BCM function causes the lamps to remain active.

Inadvertent Power Feature

Inadvertent power feature provides a similar function for the interior lamps as a retained accessory power feature. The BCM will energize the courtesy lamps supply voltage circuit when the BCM is in the active state (awake). When the courtesy lamps supply voltage circuit is energized, it supplies voltage to all the interior lights. The BCM will continue to supply voltage to the interior lamps after the ignition is turned OFF so that the interior lamps may be operated.

The inadvertent power feature will also act as battery run down protection by deactivate the courtesy lamps supply voltage circuit after 20 minutes once the BCM becomes inactive (ignition OFF and no BCM input activity.)

Theater Dimming

The theatre dimming feature that will slowly dim the interior lamps from full brightness to off. The following actions will over ride the theatre dimming feature causing the courtesy lamps to deactivate immediately if no other BCM function commands the courtesy lamps on

1. A transition from active to inactive of the interior lamps switch (turning off the interior lamps switch).
2. A LOCK command from the remote keyless entry system.
3. A last door closed locking function (locking and closing all the doors).

Courtesy Lamps Manual Operation

The courtesy lamps, may be manually operated by the IP dimmer switch. When the IP dimmer switch is placed in the ON position the BCM receives a ground from the courtesy lamp switch signal circuit. Upon receiving the courtesy lamp switch signal the BCM then pulls low the courtesy lamp low control output circuit, which illuminates the courtesy lamps. The voltage for all interior lamps is supplied by the courtesy lamp supply voltage circuit of the BCM, whenever the BCM is active. The interior lamp switch will override any BCM operation of the interior lamps, such as entry illumination.

Dome Lamp

The dome lamp is turned ON by the IP dimmer switch or during illuminated entry.

During illuminated entry or when the IP dimmer switch is ON the BCM wakes up and then energizes the courtesy lamps supply voltage circuit, suppling voltage to all interior lamps. The BCM pulls the courtesy lamps low control circuit low, providing ground to the dome lamp and all courtesy lamps.

IP Compartment Lamp

When the IP compartment is opened the IP compartment lamp illuminates, if the courtesy lamps supply voltage circuit of the BCM is activated (BCM awake).

The IP compartment lamp illuminates when the courtesy lamps supply circuit of the BCM supplies voltage to the IP compartment lamp and the IP compartment switch closes, providing a ground path.

IP Courtesy Lamp

The IP courtesy lamp is turned ON by the IP dimmer switch or during illuminated entry.

During illuminated entry or when the IP dimmer switch is ON the BCM wakes up and then energizes the courtesy lamps supply voltage circuit, suppling voltage to all interior lamps. The BCM pulls the courtesy lamp low control circuit low, providing ground to the IP courtesy lamps and all courtesy lamps.

Inside Rear View Mirror Lamp

The inside rear view mirror lamp is turned ON by the IP dimmer switch, the inside rear view mirror switch, or during illuminated entry.

During illuminated entry or when the IP dimmer switch is ON the BCM wakes up and then energizes the courtesy lamps supply voltage circuit, suppling voltage to all interior lamps. The BCM pulls the courtesy lamp low control circuit low, providing ground to the inside rear view mirror lamp and all courtesy lamps.

The inside rear view mirror lamp can be turned on from the inside rear view mirror switch. The BCM supplies voltage through the courtesy lamps supply voltage circuit when the BCM is awake. Manually turning on the inside rear view mirror switch provides a ground path.

Rear Compartment Lamp

When the rear compartment is opened, the rear compartment lamp illuminates.

When the rear compartment is opened, the rear compartment courtesy lamp switch sends a ground signal to the BCM, waking the BCM. When the BCM wakes up it will then energize the courtesy lamps supply voltage circuit, suppling voltage to the rear compartment courtesy lamp. The rear compartment courtesy lamp switch will provide a ground path for the rear compartment courtesy lamp in order to illuminate the lamp.

Roof Rail Courtesy Lamps

The roof rail courtesy lamps are turned ON by the IP dimmer switch, the individual roof rail courtesy lamp switch, or during illuminated entry.

During illuminated entry or when the IP dimmer switch is ON the BCM wakes up and then energizes the courtesy lamps supply voltage circuit, suppling voltage to all interior lamps. The BCM pulls the courtesy lamp low control circuit low, providing ground to the roof rail courtesy lamps and all courtesy lamps.

The roof rail courtesy lamps can be turned on from the individual roof rail courtesy lamp switch. The BCM supplies voltage through the courtesy lamps supply voltage circuit when the BCM is awake. Manually turning on the roof rail courtesy lamp switch provides a ground path.

Sunshade Mirror Lamps

When the vanity mirror cover on the sunshade is opened, the sunshade mirror lamp illuminates.

The sunshade mirror lamps receive voltage from the courtesy lamps supply voltage circuit anytime the BCM is awake. The sunshade illuminated mirror lamps receive ground from their individual switches when the sunshade is open.

Underhood Compartment Lamp

When the underhood compartment is opened the underhood compartment lamp illuminates, if the courtesy lamps supply voltage circuit of the BCM is activated (BCM awake).

The underhood compartment lamp illuminates when the courtesy lamps supply circuit of the BCM supplies voltage to the underhood compartment lamp and the underhood compartment switch closes, providing a ground path.

Interior Lamps Dimming

The second group of lamps include lamps which may be dimmed. This group may use a combination of vacuum fluorescent (VF) illumination and incandescent lamps

1. Ashtray lamp
2. Fog lamp switch
3. Door switches and window switches
4. HVAC control head assembly
5. Outside rear view mirror
6. Radio
7. Steering wheel controls
8. The Instrument Panel Cluster (IPC)
9. Heated seat switches
10. Traction control switch

When the autolamp switch is placed in the PARK position, battery voltage is supplied through the autolamp switch to both the TAIL LAMP, LIC LAMPS fuse and the FRONT PARK fuse. Battery voltage is then applied through the TAIL LAMP, LIC LAMPS fuse to the PANEL DIMMING fuse. From the PANEL DIMMING fuse, voltage is then applied to the I/P dimming switch. Voltage is then applied to all the dimmable lamps.

Incandescent Dimming

The incandescent lamps become illuminated when the park lamps are on. The brightness of all the incandescent lamps is determined by a variable voltage signal from the dimmer switch and sent through the instrument panel lamp supply voltage 1 circuit. The incandescent lamps are located in various components (see schematics).

Vacuum Fluorescent (VF) Dimming

The vacuum florescent lamps will be at full brightness when the ignition is on and the park lamps are off. When the park lamps are turned on, voltage is supplied by the instrument panel lamp fuse supply voltage circuit to the VF display components. The VF display will then dim to the level set by the dimmer switch. The brightness of all the vacuum florescent displays is determined by a variable voltage signal produced by the dimmer switch and sent through the instrument panel lamp supply voltage 1 circuit. With the park lamps activated, the following components will dim for night time viewing

1. The VF display of the radio
2. The HVAC module
3. The Instrument Cluster VF displays

When the instrument panel lamp fuse supply voltage is present, the VF display is at its high brightness for daytime viewing. When the park lamps are on, the VF displays receive two signals. The first from the instrument panel lamp fuse supply voltage circuit and the second from the instrument panel lamp supply voltage 1 circuit.

The Body Control Module (BCM) module processes the inputs and the controls. The ambient light sensor supplies the BCM with a signal for daytime conditions or for low light conditions

1. The Body Control Module (BCM)
2. The Instrument Panel Cluster (IPC)

Driver controls include the following components

1. The IP dimmer switch
2. The door jamb switches
3. The autolamp switch
4. The rear compartment lid ajar switch
5. The IP compartment lamp switch

See also:
• TESTING FOR INTERMITTENT AND POOR CONNECTIONS
• CHECKING AFTERMARKET ACCESSORIES
• FASTENER NOTICE
• DIAGNOSTIC SYSTEM CHECK - LIGHTING SYSTEMS
• FOG LAMP AIMING PROCEDURE