B2600

CIRCUIT DESCRIPTION
The BCM monitors the voltage on the headlamp dimmer switch high beam signal circuit in order to determine the amount of voltage present in the high beam circuit. The BCM will set DTC B2600 when either of the following conditions exists:
- The headlamp dimmer switch high beam signal circuit is shorted to battery voltage.
- The headlamp dimmer switch high beam signal circuit is shorted to ground and the daytime running lamps (DRL) are requested ON.

The BCM monitors the headlamp dimmer switch high beam signal circuit in order to determine if either of the following lamps are ON:
- The DRL
- The high beams

CONDITIONS FOR RUNNING THE DTC
- The system voltage must be between 9.0 and 16.0 volts.
- The ignition switch must be in the RUN position.
- The park brake must be released.
- The headlamp switch must be in the OFF or AUTO position.
- Daylight conditions must exist.

CONDITIONS FOR SETTING THE DTC
- The BCM commands the DRL relay ON under the following conditions:
- An open exists in the headlamp dimmer switch high beam signal circuit.
- The headlamp dimmer switch high beam signal circuit is shorted to ground.
- The headlamp dimmer switch high beam signal circuit is shorted to battery voltage.
- The system voltage is between 9.0 - 16.0 volts.
- The above conditions exist for 0.5 seconds.

ACTION TAKEN WHEN THE DTC SETS
The daytime running lamps will not operate correctly.

CONDITIONS FOR CLEARING THE MIL/DTC
- A current DTC will clear after the next ignition cycle that does not contain a fault.
- A history DTC will clear after 100 consecutive ignition cycles without a fault present.
- History and current DTCs may be cleared using a scan tool.

DIAGNOSTIC AIDS
- Always diagnose the first DTC that is listed on the scan tool.
- Verify that the scan tool displays DTC B2600 as a current code before you perform diagnostics.
- The scan tool can command the DRL relay ON. This test is located under the Special Functions menu.
- Compare the state of the DRL relay as indicated on the scan tool with the actual state of the DRL relay.
- Test for an inoperative high beam headlamp.
- Use an incandescent shop light or a flashlight. Direct the lighting toward the light sensor in order to force the light sensor into a LIGHT state.
- Inspect for loose or poor connection at all of the related components. Refer to Testing for Intermittent and Poor Connections in Diagrams.

TEST DESCRIPTION

Steps 1-6:

Steps 7-9:

Steps 10-14:

Steps 15-16:

Steps 17-27:

The numbers below refer to the step numbers on the diagnostic table.
4. This step tests the headlamp dimmer switch high beam signal circuit for a short to ground.
5. This step tests the headlamp dimmer switch high beam signal circuit for a short to battery voltage.
6. This step tests the power feed circuit for the HDLP PWR relay.
7. This step tests the HDLP PWR relay.
8. This step tests the power feed circuit to the HDLP fuses.
10. This step test the DRL relay.
15. This step tests the headlamp dimmer switch high beam signal circuit for an open or short to voltage.