Lighting Systems: Overview GMC Savana H2500

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.

Scheme 1

Scheme 2

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.

Scheme 3

Scheme 4

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 5

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.

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Scheme 7

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.

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Scheme 9

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.

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Scheme 11

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

1. 2. This step test determines if the problem exists in the DRL control/BCM or other circuitry.
2. 3. This step test determines if the problem exists in the wiring or the BCM.
3. 7. This step test determines if the problem exists in the wiring or the BCM.
4. 9. After replacement of the BCM you must calibrate the new module for proper operation.

Scheme 12

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 13

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

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

Scheme 14

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

1. 5. This step tests for an open coil in the courtesy lamp relay.
2. 8. After replacement of the BCM you must calibrate the new module for proper operation.

Scheme 15

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.

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Scheme 17

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 18