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HOMESERVICE MANUALSCHEVROLET2008CHEVY EXPRESS G2500, VAN CARGO, 6.6 6REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 666 (LIGHTING SYSTEMS)DIAGNOSTIC INFORMATION AND PROCEDURESDTC B2575TEST DESCRIPTION
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6

Test Description

2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6SECTION Test Description
WARNING: This page is about a different car, the 2006 GMC Sierra, 2006 GMC Cab & Chassis Sierra, 2006 Chevrolet Silverado, and 2006 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

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 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, including the relay coil side.
  5. 12:  After replacement of the BCM you must calibrate the new module for proper operation.
DTC B2575

Step Action Yes No
Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics 
Connector End View Reference: Lighting Systems Connector End Views  or Computer/Integrating Systems Connector End Views in Computer/Integrating Systems
1 Did you perform the Diagnostic System Check - Vehicle? Go to Step 2  Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2
  1. Turn ON the ignition, with the engine OFF.
  2. Place the headlamp switch in the ON position.
  3. Place the headlamp dimmer switch in the low beam position.
  4. Place the headlamp switch in the OFF position.
Do the low beam headlamps operate as expected?		 Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems Go to Step 3 
3
  1. Turn OFF the ignition.
  2. Disconnect the headlamp low beam relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the control circuit of the headlamp low beam relay and a good ground.
Does the test lamp illuminate?		 Go to Step 4  Go to Step 10 
4
  1. Connect a test lamp between the control circuit of the headlamp low beam relay and the battery positive voltage circuit of the headlamp low beam relay.
  2. While observing the test lamp, place the headlamp switch in the ON position, and then the OFF position.
Does the test lamp turn ON and OFF with each cycle of the switch?		 Go to Step 8  Go to Step 5 
5 Does the test lamp remain illuminated with each cycle of the switch? Go to Step 7  Go to Step 6 
6 Test the control circuit of the headlamp low beam relay for a short to voltage or an open. Refer to Circuit Testing andWiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 13  Go to Step 9 
7 Test the control circuit of the headlamp low beam relay for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 13  Go to Step 9 
8 Inspect for poor connections at the headlamp low beam relay. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 13  Go to Step 11 
9 Inspect for poor connections at the harness connector of the body control module (BCM). Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 13  Go to Step 12 
10 Repair the battery positive voltage circuit of the headlamp low beam relay. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 Go to Step 13  -
11 Replace the headlamp low beam relay. Refer to Relay Replacement (Within an Electrical Center) or Relay Replacement (Attached to Wire Harness) in Wiring Systems.
Did you complete the replacement?		 Go to Step 13  -
12 Replace the BCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.
Did you complete the replacement?		 Go to Step 13  -
13
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC reset?		 Go to Step 2  System OK
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.