Lighting Systems: Overview Chevrolet Silverado 2500

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) - Checks for BCM DTCs.
3. 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 1

Scheme 2

Scheme 3

The numbers below refer to the step number(s) on the diagnostic table.

1. 2) - Tests for the proper operation of the circuit in the low voltage range
2. 3) - 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. 4) - Tests for a short to voltage in the 5 volt reference circuit.

Scheme 4

Scheme 5

The number(s) below refer to the step number(s) on the diagnostic table.

1. 2) - Tests for the proper operation of the circuit in the low voltage range.
2. 3) - 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. 4) - Tests for a short to voltage in the 5 volt reference circuit.

The number(s) below refer to the step number(s) on the diagnostic table.

1. 2) - Listen for an audible click when the inadvertent power relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
2. 3) - Tests for voltage at the battery positive voltage circuit, coil side, of the inadvertent power relay. The CTSY LP fuse supplies voltage to the coil side of the inadvertent power relay.
3. 4) - Verifies that the body control module is providing ground to the inadvertent power relay.
4. 5) - Tests if ground is constantly being applied to the inadvertent power relay.
5. 6) - Since this is a general circuit malfunction code, it is necessary to test for both a short to voltage as well as an open on this circuit.

Scheme 6

Scheme 7

The number(s) below refer to the step number(s) on the diagnostic table.

1. 2) - OFF is the normal state of the switch before activation.
2. 4) - OFF is the normal state of the switch before activation.
3. 5) - This step tests for a short to ground on the front fog lamp switch signal circuit.
4. 6) - After replacement of the BCM you must calibrate the new module for proper operation.

The number(s) below refer to the step number(s) on the diagnostic table.

1. 2) - Listen for an audible click when the headlamp relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
2. 3) - Verifies that the body control module is providing voltage to the headlamp relay.
3. 4) - Tests for a short to ground on the headlamp relay coil supply voltage circuit.
4. 6) - After replacement of the BCM you must calibrate the new module for proper operation.

Scheme 8

The number(s) below refer to the step number(s) on the diagnostic table.

1. 2) - Command both the ON and OFF states. Repeat the commands as necessary.
2. 3) - This step determines if the condition is located in the interior lamps supply voltage circuit.
3. 4) - This step determines if the condition is located on the coil side or the switch side of the circuit.
4. 6) - This step determines if the body control module (BCM) is providing ground for the park lamp relay.
5. 7) - This step determines if a ground is constantly being applied to the park lamp relay.
6. 25) - After you replace the BCM, you must calibrate the new module for proper operation.

The number(s) below refer to the step number(s) 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 instrument panel lamp supply voltage circuit is shorted to ground.
3. 5) - Tests for a short to voltage in the battery positive voltage circuit.
4. 13) - After replacement of the BCM you must calibrate the new module for proper operation.

Scheme 9

Scheme 10

The number(s) below refer to the step number(s) on the diagnostic table.

1. 2) - Listen for an audible click when the courtesy 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 courtesy lamp relay. The CTSY fuse supplies power to the coil side of the courtesy lamp relay.
3. 4) - Verifies that the body control module is providing ground to the courtesy lamp relay.
4. 5) - Tests if ground is constantly being applied to the courtesy lamp relay.
5. 12) - After replacement of the BCM you must calibrate the new module for proper operation.

The number(s) below refer to the step number(s) on the diagnostic table.

1. 2) - Listen for an audible click when the courtesy 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 courtesy lamp relay. The CTSY fuse supplies power to the coil side of the courtesy lamp relay.
3. 4) - Verifies that the body control module is providing ground to the courtesy lamp relay.
4. 5) - Tests if ground is constantly being applied to the courtesy lamp relay.
5. 12) - After replacement of the BCM you must calibrate the new module for proper operation.

Scheme 11

The number(s) below refer to the step number(s) on the diagnostic table.

1. 2) - Listen for an audible click when the ground illumination 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 ground illumination relay. The SEO1 fuse supplies power to the coil side of the ground illumination relay.
3. 4) - Verifies that the body control module is providing ground to the ground illumination relay.
4. 5) - Tests if ground is constantly being applied to the ground illumination relay.
5. 12) - After replacement of the BCM you must calibrate the new module for proper operation.

Scheme 12

Scheme 13

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

1. 2) - Listen for an audible click when the ground illumination relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
2. 3) - Tests for voltage at the battery positive voltage side of the puddle amp relay. The SEO1 fuse supplies power to the battery positive voltage side of the ground illumination relay.
3. 4) - Verifies that the body control module is providing ground to the ground illumination relay.
4. 5) - Tests if ground is constantly being applied to the ground illumination relay.
5. 12) - After replacement of the BCM you must calibrate the new module for proper operation.

The number(s) below refer to the step number(s) on the diagnostic table.

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

Scheme 14

Scheme 15

The number(s) below refer to the step number(s) on the diagnostic table.

1. 3) - Tests for the proper operation of the ambient light sensor signal circuit in the low voltage range.
2. 4) - Tests for the proper operation of the ambient light sensor signal 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. 13) - After replacement of the BCM you must calibrate the new module for proper operation.

Scheme 16

Scheme 17

1. Perform the «Diagnostic System Check - Lighting Systems»(ref-176693-S22254214952005051000000) before using the Symptom Tables in order to verify that all of the following are true: There are no DTCs 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 the following: See «Exterior Lighting Systems Description & Operation»(ref-176693-S09398546132005051000000) . See «Interior Lighting Systems Description & Operation»(ref-176693-S16923395092005051000000) .