Test Description

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 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.

2: Listen for an audible click when the DRL relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
3: Tests for voltage at the coil side of the DRL relay.
4: Verifies that the body control module (BCM) is providing ground to the DRL relay.
5: Tests if ground is constantly being applied to the DRL relay.
6: Tests if there is opposing voltage present or an open in the DRL relay control circuit.
12: After replacement of the BCM you must calibrate the new module for proper operation.

DTC B2600

Step	Action	Yes	No
Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics Connector End View Reference: Lighting Systems Connector End Views or Body Control System Connector End Views in Body Control System.
1	Did you perform the Lighting Systems Diagnostic System Check?	Go to Step 2	Go to Diagnostic System Check - Lighting Systems
2	Install a scan tool. Turn ON the ignition, with the engine OFF. With a scan tool, command the DRL relay ON and OFF. Does the DRL relay turn ON and OFF with each command?	Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems	Go to Step 3
3	Turn OFF the ignition. Disconnect the DRL relay. Turn ON the ignition, with the engine OFF. Connect a test lamp between the battery positive voltage circuit of the DRL relay and a good ground. Does the test lamp illuminate?	Go to Step 4	Go to Step 10
4	Connect a test lamp between the control circuit and the battery positive voltage circuit of the DRL relay. With a scan tool, command the DRL relay ON and OFF. Does the test lamp turn ON and OFF with each command?	Go to Step 8	Go to Step 5
5	Does the test lamp remain illuminated with each command?	Go to Step 7	Go to Step 6
6	Test the control circuit of the DRL relay for high resistance, an open, or a short to voltage. 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
7	Test the control circuit of the DRL 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 DRL relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector 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 BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 13	Go to Step 12
10	Repair the DRL supply voltage circuit of the DRL relay. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?	Go to Step 13	-
11	Replace the DRL relay. Refer to Relay Replacement (Within an Electrical Center)Relay Replacement (Attached to Wire Harness) in Wiring Systems. Did you complete the replacement?	Go to Step 13	-
12	IMPORTANT: Perform the setup procedure for the BCM. Replace the body control module (BCM). Refer to Body Control Module Replacement in Body Control System.Did you complete the replacement?	Go to Step 13	-
13	Use the scan tool in order to clear the DTCs. 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