B3806
DTC B3806
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptor
DTC B3806 00
- High Beam and Headlamp Flash Select Circuit Malfunction
Diagnostic Fault Information
Circuit/System Description
When the turn signal/multifunction switch is placed in the high beam or flash to pass position, the body control module (BCM) will receive a ground signal through the turn signal/multi-function switch signal circuit to illuminate the high beam lamps.
Conditions for Running the DTC
High beam or flash activated.
Conditions for Setting the DTC
The body control module (BCM) reports stuck turn signal/multifunction switch.
Action Taken When the DTC Sets
The high beam function is inoperative.
Conditions for Clearing the DTC
The condition for setting the DTC is no longer present.
Reference Information
Schematic Reference
Exterior Lights Schematics Exterior Lights Schematics
Connector End View Reference
Component Connector End Views Hybrid/EV Battery Pack X1 A4
Description and Operation
Exterior Lighting Systems Description and Operation Exterior Lighting Systems
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References Control Module References
Circuit/System Verification
Ignition ON, turn the headlamp switch in the low beam position. Push/pull the turn signal/multi-function switch between the ON/OFF position. The high beam lamps should be ON/OFF as the switch is cycled.
Circuit/System Testing
1. Ignition OFF, disconnect the S78 Turn Signal/Multi-Function Switch harness connector. Test for less than 5 ohm between the ground circuit terminal 6 and ground.
• If greater then the specified value, test the ground circuit for an open/high resistance.
2. Connect the S78 Turn Signal/Multi-Function Switch harness connector.
3. Disconnect the X3 harness connector at the K9 Body Control Module.
4. Connect a test lamp between B+ and the signal circuit terminal 17 X3.
5. Pull the S78 Turn Signal/Multi-Function Switch between the flash and OFF position. The test lamp should turn ON and OFF as the switch is cycled.
• If the test lamp is always OFF, test the signal circuit for a short to voltage or an open/high resistance. If the circuit test normal, replace the S78 Turn Signal/Multi-Function Switch.
• If the test lamp is always ON, test the signal circuit for a short to ground. If the circuit test normal, replace the S78 Turn Signal/Multi-Function Switch.
6. Connect a test lamp between B+ and the signal circuit terminal 11 X3.
7. Push/pull the S78 Turn Signal/Multi-Function Switch between the high beam and OFF position. The test lamp should turn ON and OFF as the switch is cycled.
• If the test lamp is always OFF, test the signal circuit for a short to voltage or an open/high resistance. If the circuit test normal, replace the S78 Turn Signal/Multi-Function Switch.
• If the test lamp is always ON, test the signal circuit for a short to ground. If the circuit test normal, replace the S78 Turn Signal/Multi-Function Switch.
8. If all circuits test normal, replace the K9 Body Control Module.
Component Testing
Static Test
1. Ignition OFF, disconnect the S78 Turn Signal/Multi-Function Switch harness connector. S78 Turn Signal/Multi-Function Switch in flash position, test for less than 5 ohm between terminal 12 and terminal 6.
• If greater than the specified value, replace the S78 Turn Signal/Multi-Function Switch.
2. S78 Turn Signal/Multi-Function Switch in high beam position, test for less than 5 ohm between terminal 11 and terminal 6.
• If greater than the specified value, replace the S78 Turn Signal/Multi-Function Switch.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
Control Module References Control Module References for trailer brake control module replacement, programming and setup