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 momentarily placed in the flash to pass position, ground is applied to the body control module (BCM) through the flash to pass signal circuit. The BCM responds to the flash to pass request by applying ground to the high beam relay control circuit which energizes the high beam relay. With the high beam relay energized, the switch contacts close allowing battery voltage to flow through the high beam fuses to the high beam control circuits illuminating the high beam headlamps. The high beam headlamps will only illuminate for as long at the flash to pass switch is activated.

Conditions for Running the DTC

Battery voltage must be between 9-16 V.

Conditions for Setting the DTC

The BCM detects a short to ground in the turn signal/multifunction switch flash to pass signal circuit.

Actions Taken When the DTC Sets

The high beam lamps and the high beam indicator on the instrument panel cluster (IPC) are always ON.

Conditions for Clearing the DTC

* The condition responsible for setting the DTC no longer exists.
* A history DTC will clear once 100 consecutive malfunction-free vehicle ON/OFF switch cycles have occurred.

Reference Information
Schematic Reference

Exterior Lights Schematics Exterior Lights Schematics
Connector End View Reference

Component Connector End Views Hybrid/EV Battery Pack X1
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 Programming and Relearning for scan tool information

Circuit/System Testing

1. Vehicle OFF, disconnect the harness connector at the S78 turn signal/multifunction switch.
2. Vehicle OFF, scan tool disconnected, all doors closed, all accessories OFF, and wait 2 minutes. Test for less than 10 ohm between the ground circuit terminal 6 and ground.

• If greater then the specified range, test the ground circuit for an open/high resistance.

3. Vehicle in Service Mode, verify the scan tool Headlamps Flash Switch parameter is Inactive.

• If not the specified value, test the signal circuit terminal 12 for a short to ground. If the circuit tests normal, replace the K9 BCM.

4. Install a 3 A fused jumper wire between the signal circuit terminal 12 and ground. Verify the scan tool Headlamps Flash Switch parameter is Active.

• If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K9 BCM.

5. If all circuits test normal, replace the S78 turn signal/multifunction switch.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.

* Turn Signal Multifunction Switch Replacement Turn Signal Multifunction Switch Replacement
* Control Module References Programming and Relearning for BCM replacement, setup, and programming