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Diagnostic Aids

WARNING: This page is about a different car, the 2004 Pontiac Aztek and 2004 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.
DTC B2603

Step Action Yes No
Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics 
Connector End View Reference: Master Electrical Component List
1 Did you perform the Diagnostic System Check? Go to Step 2  Go to Diagnostic System Check - Lighting Systems 
2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, command the DRL relay ON and OFF.
Does the DRL relay turn ON and OFF with each command?		 Go to Diagnostic Aids Go to Step 3 
3
  1. Turn OFF the ignition.
  2. Disconnect the DRL relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the coil side supply circuit of the DRL relay with a test lamp that is connected to 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 DRL relay and the coil side supply circuit of the DRL relay.
  2. 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 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 a poor connection 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 a high resistance or a poor connection at the harness connector of the body control module (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 Replace the underhood fuse block. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Did you complete the repair?		 Go to Step 13  -
11 Replace the DRL relay. Refer to Relay Replacement (Attached to Wire Harness) or Relay Replacement (Within an Electrical Center) in Wiring Systems.
Did you complete the replacement?		 Go to Step 13  -
12
IMPORTANT: Perform the set up procedure for the body control module (BCM). Refer to Body Control Module (BCM) Programming/RPO Configuration in Body Control Systems.
Replace the BCM. Refer to Body Control Module Replacement in Body Control System.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
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