Lighting Systems: Overview Chevrolet Suburban X

Test Description

The number(s) below refer to the step number(s) 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. 3. This step determines if an ignition switch power mode condition exists. The specified procedure will determine which diagnostic path is to be followed.
3. 4. This step determines if a Body Control Module (BCM) DTC based diagnostic path or a symptom based diagnostic path are to be followed.
4. 5. 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.
5. 6. This step displays stored system related DTCs to be diagnosed.

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Scheme 155

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

1. 9. Determines if it is the headlamp on indicator circuit or the BCM.
2. 10. Determines if it is the headlamp on indicator circuit or the BCM.
3. 15. After replacement of the BCM you must calibrate the new module for proper operation.

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Scheme 157

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

1. 3. This step test determines if the problem exists in the wiring or the BCM.
2. 5. After replacement of the BCM you must calibrate the new module for proper operation.

Scheme 158

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

1. 2. Listen for an audible click when the front fog lamp relay operates. Depress the switch for both the ON and OFF states. Repeat as necessary.
2. 3. Tests for voltage at the coil side of the front fog lamp relay.
3. 4. Verifies that the body control module (BCM) is providing ground to the front fog lamp relay.
4. 5. Tests if ground is constantly being applied to the front fog lamp relay.
5. 6. Tests if there is opposing voltage present or an open in the front fog lamp relay control circuit.
6. 12. After replacement of the BCM you must calibrate the new module for proper operation.

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Scheme 160

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

1. 2. Listen for an audible click when the rear fog lamp relay operates. Depress the switch for both the ON and OFF states. Repeat as necessary.
2. 3. Tests for voltage at the coil side of the rear fog lamp relay.
3. 4. Verifies that the body control module (BCM) is providing ground to the rear fog lamp relay.
4. 5. Tests if ground is constantly being applied to the rear fog lamp relay.
5. 6. Tests if there is opposing voltage present or an open in the rear fog lamp relay control circuit.
6. 12. After replacement of the BCM you must calibrate the new module for proper operation.

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Scheme 162

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

1. 3. This step test determines if the problem exists in the wiring or the BCM.
2. 4. This step test determines if the problem exists in the wiring or the BCM.
3. 5. After replacement of the BCM you must calibrate the new module for proper operation.

Scheme 163

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

1. 3. Tests for voltage at the voltage supply side of the headlamp low beam relay.
2. 4. Verifies that the body control module (BCM) is providing ground to the headlamp low beam relay.
3. 5. Tests if ground is constantly being applied to the headlamp low beam relay.
4. 6. Tests if there is opposing voltage present or an open headlamp low beam relay control circuit.
5. 12. After replacement of the BCM you must calibrate the new module for proper operation.

Scheme 164

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

1. 2. Listen for an audible click when the high beam relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
2. 3. Tests for voltage at the coil side of the high beam relay.
3. 4. Verifies that the body control module (BCM) is providing ground to the high beam relay.
4. 5. Tests if ground is constantly being applied to the high beam relay.
5. 6. Tests if there is opposing voltage present or an open high beam relay control circuit.
6. 12. After replacement of the BCM you must calibrate the new module for proper operation.

Scheme 165

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. Tests for voltage at the coil side of the park lamp relay.
3. 4. Verifies that the body control module (BCM) is providing ground to the park lamp relay.
4. 5. Tests if ground is constantly being applied to the park lamp relay.
5. 6. Tests if there is opposing voltage present or an open park lamp relay control circuit.
6. 12. After replacement of the BCM you must calibrate the new module for proper operation.

Scheme 166

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

1. 2. Listen for an audible click when the DRL relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
2. 3. Tests for voltage at the coil side of the DRL relay.
3. 4. Verifies that the body control module (BCM) is providing ground to the DRL relay.
4. 5. Tests if ground is constantly being applied to the DRL relay.
5. 6. Tests if there is opposing voltage present or an open in the DRL relay control circuit.
6. 12. After replacement of the BCM you must calibrate the new module for proper operation.

Scheme 167

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

1. 5. This step test determines if the problem exists in the headlamp switch or the BCM.
2. 10. After replacement of the BCM you must calibrate the new module for proper operation.

Scheme 168

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

1. 3. This step test determines if the problem exists in the wiring or the BCM.
2. 4. This step test determines if the problem exists in the wiring or the BCM.
3. 5. After replacement of the BCM you must calibrate the new module for proper operation.

Scheme 169

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

1. 3. Tests for the proper operation of the circuit in the low voltage range.
2. 4. Tests for the proper operation of the circuit in the high voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to ground.
3. 5. Tests for a short to voltage in the 5 volt reference circuit.
4. 6. Tests for a high resistance or an open in the dimming return circuit.

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Scheme 171

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

1. 4. After replacement of the BCM you must calibrate the new module for proper operation.

Scheme 172

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

1. 3. Tests for the proper operation of the circuit in the low voltage range.
2. 4. Tests for the proper operation of the circuit in the high voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to ground.
3. 5. Tests for a short to voltage in the ambient light sensor low reference circuit.
4. 13. After replacement of the BCM you must calibrate the new module for proper operation.

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Low Voltage Operation of HID Headlamps

The body control module (BCM) monitors the vehicle's system voltage while in the RUN power mode. When the system voltage drops below 8.9 volts, the following will occur

STAGE 1

If the low beam headlamps are ON, either manually or automatically, the BCM will turn ON the high beam headlamps by activating it's High Beam output.

STAGE 2

When the system voltage drops below 8.5 volts, the following will occur

1. If the low beam headlamps are currently ON, either manually or automatically, the BCM will turn OFF the low beam headlamps by deactivating it's Low Beam output.
2. If the headlamps are then turned ON manually, the manual switch redundancy will cause the low beam headlamps to remain on.

If during the same ignition cycle, the BCM enters either STAGE 1 or STAGE 2 operations noted above, and then determines that the system voltage has risen, the following will occur

1. If the BCM has entered STAGE 2 operation, it will not return to STAGE 1 operation until the system voltage rises above 9.4 volts.
2. If the BCM has entered STAGE 1 operation, it will not return to normal operation until the system voltage rises above 9.8 volts.