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

Diagnostic Fault Information





Circuit/System Description

When the turn signal/multifunction switch is placed in the headlamps high or flash to pass position, ground is applied to the body control module (BCM) through the headlamp high beam signal circuit or the flash to pass switch signal circuit. The BCM applies ground to the headlamp 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 headlamps.

Conditions for Running the DTC

* Battery voltage must be between 9-16 V.
* Headlamps ON.

Conditions for Setting the DTC

The BCM detects a short to ground on the Flash to Pass switch signal circuit.

Actions Taken When the DTC Sets

When DTC B3806 is present, flash to pass will not operate.

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 ignition cycles have occurred.

Reference Information
Schematic Reference

Headlights Schematics (Headlights Schematics)
Connector End View Reference

Component Connector End Views (Connector End Views By Name)
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. Ignition OFF, disconnect the harness connectors at the S78 turn signal/multifunction switch.
2. Ignition OFF, test for less than 5 ohm between the ground circuit terminal 3 and ground.

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

3. Ignition ON, verify the scan tool Headlamp Flash Switch parameter is Inactive.

• If not the specified value, test the signal circuit terminal 4 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 4 and ground. Verify the scan tool Flash to Pass 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, test or 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