Lighting Systems: Overview Chevrolet TrailBlazer I

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.
6. 7. This step will display a stored system related DTC to be diagnosed.

Scheme 93

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Scheme 100

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

1. 3. Tests for an open in the TBC 5 battery positive voltage supply circuit within the body wiring harness extension harness.
2. 4. Tests for voltage at the LED dimming signal circuit.
3. 5. Tests for voltage at the LED dimming signal circuit when the headlamp switch is in the OFF position.
4. 11. After replacement of the BCM you must calibrate the new module for proper operation.

Scheme 101

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

1. 2. This step test determines if an open or short to ground exists.
2. 3. This step test determines if a short to ground exists in the lamp wiring or internally within the BCM.
3. 4. This step test determines if an open exists in the body wiring harness extension harness or internally within the BCM.
4. 8. After replacement of the BCM you must calibrate the new module for proper operation.

Scheme 102

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. Command both the ON and OFF states. Repeat the commands 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.

Scheme 103

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. Command both the ON and OFF states. Repeat the commands 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.

Scheme 104

Scheme 105

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

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

Scheme 106

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

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

Scheme 107

Scheme 108

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 109

Scheme 110

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 111

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

1. 2. This step test determines by process of elimination which, if any, dimmable component is causing the DTC to set.
2. 3. 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 112

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

1. 2. This step test determines if the problem exists in the wiring.
2. 3. This step test determines if an open exists in the body wiring harness extension harness.
3. 7. After replacement of the BCM you must calibrate the new module for proper operation.

Scheme 113

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 low reference circuit.

Scheme 114

Scheme 115

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

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

Scheme 116

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

1. 2. Verifies that the value displayed is within the specified range.
2. 3. Tests for the proper operation of the circuit in the high voltage range.
3. 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 voltage.

Scheme 117