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DTC B3806

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    • Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC B3806 00: Main Beam and Headlamp Flash Select Circuit Malfunction

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Indicator/Multifunction Switch Headlamps OFF Signal

B257A 00

1

1

--

Indicator/Multifunction Switch Headlamps ON Signal

B257A 00

1

1

--

Indicator/Multifunction Switch Sidelights ON Signal

2

B257A 00

2

--

Indicator/Multifunction Switch Flash To Pass Signal

3806 00

1

1

--

Indicator/Multifunction Switch Main Beam Signal

B3650 08

1

1

--

Indicator/Multifunction Switch Ground

--

1

--

--

1. Headlamps Malfunction

2. Sidelight, Number Plate, and/or Tail Lamps Malfunction

Circuit/System Description

When the indicator/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 energises the main beam relay. With the main beam relay energised, the switch contacts close allowing battery voltage to flow through the main beam fuses to the main beam control circuits illuminating the main beam headlamps. The main 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 9-16V.

Conditions for Setting the DTC

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

Action Taken When the DTC Sets

The main beam lamps and the main beam indicator on the instrument panel cluster 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 Lamps Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Testing
  1. Vehicle OFF, disconnect the harness connector at the S78 Indicator/Multifunction Switch.
  2. Vehicle OFF, scan tool disconnected, all doors closed, all accessories OFF, and wait 2 minutes. Test for less than 10 Ω between the ground circuit terminal 6 and ground.
    3. ⇒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.
    4. ⇒If not the specified value, test the signal circuit terminal 12 for a short to ground. If the circuit tests normal, replace the K9 Body Control Module.
  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.
    5. ⇒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 Body Control Module.
  5. If all circuits test normal, replace the S78 Indicator/Multifunction Switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Turn Signal Multifunction Switch Replacement
    • Control Module References for BCM replacement, programming and setup
   


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