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The daytime running lamps (DRL) are controlled by the body control module (BCM). The BCM Reference Information Schematic Reference Fog Lights Schematics Connector End View Reference Component Connector End Views Description and Operation Exterior Lighting Systems Description and Operation Electrical Information Reference Circuit Testing Connector Repairs 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, observe the scan tool Ambient Light Sensor parameter voltage while carefully supplying sufficient light to simulate daylight conditions to the ambient light sensor, then If the reading does not change between light and dark, refer to the Ambient Light 2. Connect a test lamp between the relay side of the DRL fuse and ground. 3. Verify that the test lamp turns on and off while commanding the daytime running lamps ON and OFF with a scan tool.
2008 Chevrolet Silverado 1500 2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
If the test lamp does not turn on and off while changing between the commanded 4. If 1 or both of the daytime running lamps do not turn on and off, refer to the Daytime Running Lamps Circuit Test below. Circuit/System Testing Ambient Light Sensor Circuit Test 1. Ignition OFF, disconnect the harness connector at the ambient light sensor. 2. Ignition OFF, test for less than 1 ohm of resistance between the listed ground circuit terminal and ground. Ambient light sensor terminal B Ambient light/sunload sensor terminal C If greater than the specified range, test the ground circuit for an open/high resistance. 3. Ignition ON, verify the scan tool ambient light sensor parameter is greater than 4.5 volts. If less than the specified range, test the signal circuit for a short to ground. If the circuit 4. Install a 3A fused jumper wire between the listed signal circuit terminal and the low reference circuit terminal. Verify the scan tool light sensor parameter is less than 1.0 volt. Ambient light sensor terminal A to B Ambient light/sunload sensor terminal D to C If greater than the specified range, test the signal circuit for a short to voltage or an 5. If all circuits test normal, test or replace the ambient light sensor. DRL Relay Control Circuit Test 1. Ignition OFF, disconnect the harness connector X4 at the BCM. 2. Ignition ON, verify the daytime running lamps are not on. If the daytime running lamps are on, test the DRL relay control circuit for a short to 3. Install a 10A fused jumper wire between the relay control circuit terminal 23 and ground. Verify the daytime running lamps are on. are on. If the daytime running lamps are not on, test the DRL relay control circuit for an 4. If all circuits test normal, replace the BCM.
2008 Chevrolet Silverado 1500 2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
Daytime Running Lamps Circuit Test 1. Ignition OFF, disconnect the harness connector at the affected headlamp. 2. Test for less than 1 ohm of resistance between the ground circuit terminal B 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 A and the ground circuit terminal B. 4. Command the daytime running lamps on and off with a scan tool. The test lamp should turn on and off when changing between the commanded states. If the test lamp is always on, test the control circuit for a short to voltage. If the circuit If the test lamp is always off, test the control circuit for a short to ground or an 5. If all circuits test normal, test or replace the affected headlamp. Repair Procedures Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Ambient Light Sensor Replacement Headlamp Bulb Replacement (GMC) or Headlamp Bulb Replacement (Chevrolet) Underhood Electrical Center or Junction Block Replacement Control Module References for BCM replacement, programming, and setup. EXTERIOR COURTESY 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. Circuit/System Description The exterior courtesy lamps are supplied with the courtesy lamp supply voltage from the driver Reference Information
2008 Chevrolet Silverado 1500 2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
Schematic Reference Exterior Lights Schematics Connector End View Reference Component Connector End Views Description and Operation Exterior Lighting Systems Description and Operation Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs Scan Tool Reference Control Module References for Scan Tool Information Circuit/System Verification Ignition ON, command the Puddle/Courtesy Lamp ON and OFF with a scan tool. Verify the Circuit/System Testing 1. Disconnect the harness connector at the affected courtesy lamp bulb. 2. Ignition ON, verify that a test lamp illuminates between the courtesy lamp supply circuit terminal and ground. If the test lamp does not illuminate, test the courtesy lamp supply circuit for a short to 3. Connect a test lamp between the low side control circuit terminal and the courtesy lamp supply circuit terminal. 4. Command the Puddle/Courtesy Lamp ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to ground. If the
2008 Chevrolet Silverado 1500 2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
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