Circuit Description
The daytime running lamps (DRL) are controlled by the body control module (BCM). The BCM grounds the DRL relay control circuit in order to energize the DRL relay coil. This action provides a path to ground for the RH and LH headlamps through the DRL relay and the DRL resistor. The DRL resistor reduces the intensity of the low beam headlamps for DRL operation. The BCM monitors the low beam circuit to ensure that the DRL are operating properly.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B2600 Daytime Running Lamp Control Circuit
Conditions for Running the DTCs
| • | The ignition switch is in the RUN position. |
| • | The headlamp switch is in the AUTO position. |
| • | The park brake is not applied. |
| • | The gear selector is not in the PARK position. |
Conditions for Setting the DTC
Any of the following conditions will set this DTC:
| • | The DRL resistor supply voltage circuit is open, or shorted to ground. |
| • | The headlamp low beam signal circuit between a headlamp and the underhood fuse block is open or shorted to ground. |
| • | The battery positive voltage circuit to the headlamp is open or shorted to ground. |
| • | One of the headlamp fuses in the underhood fuse block are open . |
| • | The DRL resistor ground circuit is open. |
| • | The DRL resistor is open or shorted. |
| • | The DRL relay is stuck in the OPEN position. |
Action Taken When the DTC Sets
The BCM turns off the DRL relay control for the remainder of the ignition cycle.
Conditions for Clearing the DTC
| • | The BCM receives the clear code command from the scan tool. |
| • | A current DTC will clear when the conditions for setting the DTC are no longer present. |
| • | A history DTC clears after 100 malfunction-free ignition cycles. |
Diagnostic Aids
| • | Check both the LH and RH headlamps for proper operation. |
| • | Check both the LT HDLP and RT HDLP fuses. |
| • | If the DTC is a history DTC, the problem may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections . |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 |
Do both low beam headlamps illuminate properly? | -- | Go to Step 4 | Go to Step 3 |
3 | Test the headlamp low beam signal circuit and the battery positive voltage circuit for short to ground, high resistance or open between the headlamp and the instrument panel (I/P) fuse block. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 10 |
4 |
Is the resistance within the specified range? | 0.4-1 ohms | Go to Step 5 | Go to Step 8 |
5 | Test the DRL relay for continuity between the coil sides of the relay. Is continuity present? | -- | Go to Step 6 | Go to Step 13 |
6 | Connect a test lamp between the DRL relay control circuit of the DRL relay and ground. Does the test lamp illuminate? | -- | Go to Step 14 | Go to Step 7 |
7 |
Does the test lamp turn on and off as commanded? | -- | Go to Step 13 | Go to Step 11 |
8 | Test the DRL relay resistor supply voltage circuit of the DRL resistor for a short to ground, high resistance or an open. Refer to Circuit Testing and Wiring Repairs . Did you find and fix the concern? | Go to Step 19 | Go to Step 9 | |
9 | Test the ground circuit of the DRL resistor for high resistance or an open. Refer to Circuit Testing and Wiring Repairs . Did you find and fix the concern? | Go to Step 19 | Go to Step 12 | |
10 | Inspect for poor connections at the harness connector of the headlamp. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 19 | Go to Step 15 | |
11 | Inspect for poor connections 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 19 | Go to Step 18 |
12 | Inspect for poor connections at the harness connector of the DRL resistor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 16 |
13 | Inspect for poor connections 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 19 | Go to Step 17 |
14 | Repair a short to voltage in the DRL relay control circuit of the BCM. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 19 | -- |
15 | Replace headlamp bulb. Refer to Headlamp Assembly or Headlamp Bulb and/or Cornering, Sidemarker, Park, Turn Signal Bulb Replacement . Did you complete the replacement? | Go to Step 19 | -- | |
16 | Replace the DRL resistor. Refer to Daytime Running Lamps (DRL) Resistor Replacement . Did you complete the replacement? | -- | Go to Step 19 | -- |
17 | Replace the DRL relay. Refer to Relay Replacement . Did you complete the replacement? | -- | Go to Step 19 | -- |
18 | Replace the BCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 19 | -- |
19 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
