Circuit Description
The body control module (BCM) controls the daytime running lamp (DRL) relay by grounding the control circuit of the DRL relay coil.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B2602 Daytime Running Lamp Control Circuit Low
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. |
Conditions for Setting the DTC
| • | The BCM detects a short to ground or an open in the control circuit of the DRL relay coil when the daytime running lamps are inactive. |
| • | The condition must be present for more than 3 ms. |
Action Taken When the DTC Sets
| • | The BCM stores DTC B2602 in memory. |
| • | The BCM may store DTC B3857 in memory. |
| • | The SERVICE VEHICLE SOON telltale illuminates. |
Conditions for Clearing the DTC
| • | A current DTC B2602 clears if the BCM no longer detects a short to ground or an open in the control circuit of the DRL relay coil. |
| • | A current DTC B3857 clears if the BCM no longer detects a short to ground in the DRL relay control circuit. |
| • | A history DTC B2602 clears after 100 consecutive ignition cycles. |
| • | The BCM receives the Clear Code commend from the scan tool. |
Diagnostic Aids
| • | If the DTC B2602 is a history DTC, the fault may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections . |
| • | An intermittent short to ground or an open 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 - Vehicle? | Go to Step 2 | |
2 |
Does the daytime running lamp (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 poor connection or an open. Refer to Circuit Testing and Wiring Repairs . 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 . 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 . 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 . 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 . Did you complete the repair? | Go to Step 13 | -- |
11 | Replace the DRL relay. Refer to Relay Replacement . Did you complete the replacement? | Go to Step 13 | -- |
12 | Replace the BCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 13 | -- |
13 |
Does the DTC reset? | Go to Step 2 | System OK |
