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Chevrolet Silverado / GMC Sierra. Manual - part 2485
Testing for Intermittent Conditions and Poor Connections
Wiring Repairs
Scan Tool Reference
Control Module References for Scan Tool Information
Circuit/System Verification
1. Ignition ON, command the Courtesy Lamps output control on and off with the scan tool.
The interior courtesy lamps should turn on and off.
If one or more of the courtesy lamps are always on or always off refer to the courtesy
lamp control circuit test below.
2. Observe the scan tool BCM, Driver Door Open Sw. parameter while opening and closing
the driver door. The reading should change between Open and Closed.
If the Driver Door Open Sw. parameter does not change between Open and Closed,
refer to Driver Door Open Switch Test below.
3. Observe the scan tool BCM, Passenger Door Open Sw. parameter while opening and
closing the front passenger door. The reading should change between Open and Closed.
If the Passenger Door Open Sw. parameter does not change between Open and Closed,
refer to Passenger Door Open Switch Test below.
4. Observe the scan tool BCM Passenger Door Open Sw. parameter while opening and closing
each rear doors one at a time. The reading should change between Open and Closed.
If the Ctsy. Lamp Actv. Reason parameter does not change between Open and Closed,
refer to Passenger Door Open Switch Test below.
5. Ignition ON and all doors closed, observe the scan tool BCM Ctsy. Lamp Actv. Reason
parameter while turning the dome lamp switch ON and OFF. The reading should change
between Off and Manual.
If the Ctsy. Lamp Actv. Reason parameter does not change between Off and Manual,
refer to Dome/Interior Lamp Switch Test below.
6. Ignition ON and all doors closed, observe the scan tool BCM Ctsy. Lamp Actv. Reason
parameter while turning the interior lamp defeat switch ON and OFF. The reading should
change between Off and Manual Defeat.
If the Ctsy. Lamp Actv. Reason parameter does not change between Off and Manual,
refer to Dome/Interior Lamp Switch Test below.
Circuit/System Testing
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
Courtesy Lamp Control Circuit Test
1. Ignition OFF, disconnect the harness connector at an affected lamp bulb.
2. Test for less than 1 ohm of resistance between the ground circuit terminal and ground.
If greater than the specified range, test the ground circuit for an open/high resistance.
3. Connect a test lamp between the control circuit terminal and the ground circuit terminal.
4. Ignition ON, command the Courtesy Lamps output control on and off with the scan tool.
The test lamp should turn on and off.
If the test lamp is always ON, test the control circuit for a short to voltage. If the
circuit tests normal, replace the BCM.
If the test lamp is always OFF, test the control circuit for a short to ground or an
open/high resistance. If the circuit tests normal, replace the BCM.
5. If all circuits test normal, test or replace the bulb.
Driver Door Open Switch Test
1. Ignition OFF, disconnect the harness connector at the door latch.
2. Test for less than 1 ohm of resistance between the listed ground circuit terminal and ground.
With power door locks terminal 8
With out power door locks terminal 6
If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool driver door open switch parameter is Closed.
If not the specified value, test the listed signal circuit terminal for a short to ground. If
the circuit tests normal, replace the affected door switch.
With power door locks terminal 7
With out power door locks terminal 5
4. Install a 3A fused jumper wire between the listed signal circuit terminal and low reference
circuit terminal. Verify the scan tool door open switch parameter is active.
With power door locks terminal 7 to terminal 8
With out power door locks terminal 6 to terminal 5
If not the specified value, test the signal circuit for a short to voltage or an open/high
resistance. If the circuit tests normal, replace the driver door switch.
5. If all circuits test normal, test or replace the driver door latch.
Passenger Door Open Switch Test
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
1. Ignition OFF, disconnect the harness connector at the affected door latch.
2. Test for less than 1 ohm of resistance between the listed ground circuit terminal and ground.
Left terminal 6
Right terminal 3
If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool passenger door open switch parameter is Closed.
If not the specified value, test the listed signal circuit terminal for a short to ground. If
the circuit tests normal, replace the BCM.
Left terminal 5
Right terminal 2
4. Install a 3A fused jumper wire between the listed signal circuit terminal and low reference
circuit terminal. Verify the scan tool passenger door open switch parameter is Open.
Left terminal 5 to terminal 6
Right terminal 2 to terminal 3
If not the specified value, test the signal circuit for a short to voltage or an open/high
resistance. If the circuit tests normal, replace the BCM.
5. If all circuits test normal, test or replace the affected door latch.
Dome/Interior Lamp Switch Test
1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Test for less than 1 ohm of resistance between the ground circuit terminal 8 and ground.
If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool Ctsy. Lamp Actv. Reason parameter is Off.
If not the parameter is Manual or Manual Defeat, test the affected signal circuit
terminal for a short to ground. If the circuit tests normal, replace the BCM.
Manual terminal 12
Manual Defeat terminal 9
4. Install a 3A fused jumper wire between the signal circuit terminal 12 and the ground circuit
terminal 8. Verify the scan tool Ctsy. Lamp Actv. Reason parameter is Manual.
If not the specified value, test the signal circuit for a short to voltage or an open/high
resistance. If the circuit tests normal, replace the BCM.
5. Install a 3A fused jumper wire between the signal circuit terminal 9 and the ground circuit
terminal 8. Verify the scan tool Ctsy. Lamp Actv. Reason parameter is Manual Defeat.
If not the specified value, test the signal circuit for a short to voltage or an open/high
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
resistance. If the circuit tests normal, replace the BCM.
6. If all circuits test normal, test or replace the headlamp switch.
Repair Procedures
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Dome Lamp Replacement
Front Side Door Lock Replacement
Rear Door Lock Replacement (Extended Cab Upper) or Rear Door Lock
Replacement (Crew Cab) or Rear Door Lock Replacement (Extended Cab Lower)
Headlamp Switch Replacement (without RPO SLT) or Headlamp Switch
Replacement (with RPO SLT)
Control Module References for BCM, driver door switch, or passenger door switch
replacement, programming, and setup.
DAYTIME RUNNING LAMPS MALFUNCTION
Diagnostic Instructions
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
Review Strategy Based Diagnosis for an overview of the diagnostic approach.
Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
Circuit
Short to
Ground
Open/High
Resistance
Short to
Voltage
Signal
Performance
Ambient Light Sensor Signal
B2645 03
B2645 07
B2645 07
-
DRL Relay Control
1
2
B2600 00
-
Low Beam Headlamp Control
4
4
3
-
Low Beam Headlamp Ground
-
4
-
-
Ambient Light Sensor Ground
-
B2645 07
-
-
1. The daytime running lamps are always on.
2. The daytime running lamps are inoperative.
3. The low beam headlamps are always on.
4. The low beam headlamps are inoperative.
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
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