Circuit Description
The body control module (BCM) controls the DRL relay by grounding the control circuit of the DRL relay coil.
Conditions for Running the DTC
| • | Voltage supplied to the module is in the normal operating voltage range (approximately 10-16 volts). |
| • | The DRL feature must be enabled. |
| • | The DRLs must be commanded ON. |
Conditions for Setting the DTC
| • | The BCM detects a short to battery positive voltage in the control circuit of the DRL relay coil when the DRLs are ON. |
| • | The condition above must be present for more than 3 ms. |
Action Taken When the DTC Sets
| • | The BCM stores DTC B2603 in memory. |
| • | The SERVICE VEHICLE SOON telltale illuminates. |
Conditions for Clearing the DTC
| • | A current DTC B2603 clears if the BCM no longer detects a short to battery positive voltage in the control circuit of the DRL relay coil. |
| • | A history DTC B2603 clears after 100 consecutive ignition cycles. |
| • | The BCM receives the Clear Code commend from the scan tool. |
Diagnostic Aids
| • | If the DTC B2603 is a history DTC, the fault may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
| • | An intermittent short to voltage in the following locations may cause an intermittent malfunction to occur: |
| - | The control circuit of the DRL relay coil |
| - | The DRL relay |
| - | The BCM |
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 | |
2 |
Does the DRL relay turn ON and OFF with each command? | Go to Diagnostic Aids | Go to Step 3 |
3 |
Does the test lamp illuminate? | Go to Step 4 | Go to Step 10 |
4 |
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 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 |
Does the DTC reset? | Go to Step 2 | System OK |
