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DTC B3650

DTC B3650

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 B3650 08

High Beam Request Signal Circuit Performance - Signal Invalid

Diagnostic Fault Information

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performance
Headlamp High Beam Signal B3650 08 1 1 -
Headlamp Flash To Pass Signal B3806 00 2 2 -
Turn Signal/Multifunction Switch Ground - 1, 2 - -
1. Headlamp Dimmer Switch Malfunction 2. Headlamp Flash To Pass Switch Malfunction


Circuit/System Description

The BCM monitors the voltage level within the high beam signal circuit and the flash to pass signal circuit. When the turn signal/multifunction switch is moved to the high beam position or to the flash to pass position, the voltage within the appropriate signal circuit drops to less than 1 V. The BCM will detect the voltage drop and will command the headlamp high beams to turn ON or OFF.

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 headlamp high beam signal circuit.

Action Taken When the DTC Sets

The high beam headlamps will malfunction.

Conditions for Clearing the DTC


• The DTC will be current for as long as the fault is present.

• When the fault is no longer present, the DTC will be a history DTC.

• A history DTC will clear after 50 ignition cycles.


Reference Information

Schematic Reference

Headlights/Daytime Running Lights (DRL) 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 Verification

Ignition ON, observe the scan tool High Beam Select Switch parameter while pulling and releasing the turn signal/multi-function switch. The value should change between Inactive and Active when changing between the selected states.

Circuit/System Testing


1. Ignition OFF, disconnect at the S78 turn signal/multifunction switch.

2. Ignition ON, verify that the scan tool High Beam Select Switch parameter is Inactive.

3. If not the specified value, test the signal circuit terminal 2 for a short to ground. If the circuit tests normal, replace the K9 BCM.

4. Connect a 3 A fused jumper wire between the signal circuit terminal 2 and ground. Verify that the scan tool High Beam Select 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 BCM.

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


Component Testing


Turn Signal/Multifunction Switch Test

1. Ignition OFF, disconnect the harness connector at the S78 turn signal/multifunction switch.

2. Test for Infinite resistance between the terminals listed below with the switch in the open position.

• Signal terminal 2 and ground terminal 3

• Signal terminal 4 and ground terminal 3

3. If not the specified value, replace the S78 turn signal/multifunction switch.

4. Test for less than 2 Ω between the signal terminal 2 and the ground terminal 3 with the switch in the high beam position.

5. If greater than the specified value, replace the S78 turn signal/multifunction switch.

6. Test for less than 2 Ω between the signal terminal 4 and the ground terminal 3 while holding the switch in the flash to pass position.

7. If greater than the specified value, replace the S78 turn signal/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