Cruze

DTC B2740

The front fog lamp relay is supplied with battery voltage at all times. The front fog lamp switch signal circuit is grounded through a resistor momentarily by pressing the front fog lamp switch. The body control module (BCM) energises the front fog lamp relay by applying ground to the front fog lamp relay control circuit. When the front fog lamp relay is energised, the relay switch contacts close and battery voltage is applied through the front fog lamp fuse to the front fog lamp supply voltage circuit which illuminates the front fog lamps.

Front fog lamp switch stuck.

The front fog lamps are inoperative.

The condition for setting the DTC is not longer present.

Schematic Reference

Fog Lamps Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, observe the scan tool Front Fog Lamps Switch parameter. The reading should change between Active/Inactive when changing between pressed and released front fog lamp switch button.

1. Ignition OFF, disconnect the X1 and X3 harness connector at the K9 Body Control Module.
2. Ignition ON, test for less than 0.3 V at the K9 Body Control Module signal circuit harness connector X1 terminal 9 and ground.

⇒	If greater then the specified value, test the signal circuit for an short to voltage.

3. Test for less than 0.3 V at the K9 Body Control Module 12 V reference circuit harness connector X3 terminal 4 and ground.

⇒	If greater than the specified value, test the 12 V reference circuit for a short to voltage.

4. Disconnect wiring harness connector of the following components:

•	K82 Mobile Telephone Control Module

•	X85 Steering Wheel Air Bag Coil

5. Ignition OFF, test for infinite resistance between the K9 Body Control Module signal circuit harness connector X1 terminal 9 and ground.

⇒	If lower than the specified value, test the signal circuit for a short to ground.

6. Test for infinite resistance between the K9 Body Control Module 12 V reference circuit harness connector X3 terminal 4 and ground.

⇒	If lower than the specified value, test the 12 V reference circuit for a short to ground.

7. Press and hold the front fog lamp switch button.
8. Test for 2.5-3.0 kΩ between the K9 Body Control Module 12 V reference circuit harness connector X3 terminal 4 and the K9 Body Control Module signal circuit harness connector X1 terminal 9.

⇒	If not within the specified range, test the 12 V reference circuit and the signal circuit for an open/high resistance. If the circuits test normal replace the S30 Headlamp Switch.

9. If all circuits test normal, replace the K9 Body Control Module.

Dynamic Test

Ignition OFF, disconnect the harness connector at the S30 Headlamp Switch. Press and hold the front fog lamp switch button, test for 2.5-3.0 kΩ at the S30 Headlamp Switch terminal 1 and terminal 12.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.