Pinpoint Test C: The Low Beam(s) Are Always On
Headlamps
Pinpoint Tests
Pinpoint Test C: The Low Beam(s) Are Always On
Refer to Wiring Diagram Set 85, Headlamps/Autolamps for schematic and connector information. Diagrams By Number
Normal Operation
The Steering Column Control Module (SCCM) sends voltage signals to the headlamp switch through the headlamp switch input circuits (off, parking lamps, headlamps). At any given time, the headlamp switch routes one of the input circuits to ground, indicating the headlamp switch position to the SCCM. The SCCM sends a message to the Body Control Module (BCM) over the High Speed Controller Area Network (HS-CAN), indicating the headlamp switch position. When the BCM receives a message from the SCCM indicating the headlamp switch in the HEADLAMPS ON position, the BCM provides voltage to the LH and RH low beams.
If the SCCM detects multiple or no active headlamp switch inputs, the BCM receives a message from the SCCM indicating a fault with the headlamp switch input and the BCM defaults the parking lamps and headlamps on.
If the BCM loses communication with the SCCM, the BCM defaults the parking lamps and headlamps on.
- DTC B10A6:09 (Main Light Switch: Component Failure) - a continuous and on-demand DTC that sets when the SCCM detects a fault from the headlamp switch input circuit(s).
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Headlamp switch
- SCCM
- BCM
PINPOINT TEST C: THE LOW BEAM(S) ARE ALWAYS ON
NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
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C1 CHECK THE COMMUNICATION NETWORK
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: Network Test.
- Carry out the network test.
- Does the SCCM module pass the network test?
Yes
If equipped with autolamps, GO to C2. If not equipped with autolamps, GO to C4.
No
REFER to Module Communications Network Testing and Inspection.
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C2 CHECK FOR LIGHT SENSOR DTCs
- Review the DTCs recorded from the BCM self-test.
- Is DTC B1A85:11 or DTC B1A85:13 present?
Yes
GO to Pinpoint Test H Pinpoint Test H: The Autolamps Are On Continuously.
No
GO to C3.
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C3 CHECK THE SCCM AUTOLAMP ON REQUEST PID
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: SCCM DataLogger.
- While placing the headlamp switch in the AUTOLAMPS ON and then OFF position, monitor the SCCM headlamp switch PID (EXT_LMP_SW).
- Does the PID agree with the headlamp switch when it is in the AUTOLAMPS ON position and indicate it is not in the AUTOLAMPS ON position when the headlamp switch is in the OFF position?
Yes
GO to C4.
No
GO to Pinpoint Test H Pinpoint Test H: The Autolamps Are On Continuously.
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C4 CHECK THE SCCM HEADLAMP SWITCH PIDs
NOTE: Make sure the headlamp switch is aligned in the correct position when monitoring the PID.
- Enter the following diagnostic mode on the scan tool: SCCM DataLogger.
- While moving the headlamp switch through all positions (OFF, PARKING LAMPS and HEADLAMPS), monitor the SCCM headlamp switch input PID (EXT_LMP_SW).
- Do the headlamp switch positions agree with the PID?
Yes
GO to C9.
No
GO to C5.
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C5 CHECK FOR VOLTAGE TO THE HEADLAMP SWITCH
- Ignition OFF.
- Disconnect: Headlamp Switch C205.
- Measure the voltage between the headlamp switch, harness side and ground as follows:
- Are the voltages greater than 5 volts?
Yes
GO to C6.
No
GO to C7.
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C6 CHECK THE HEADLAMP SWITCH GROUND CIRCUIT FOR AN OPEN
- Measure the voltage between the headlamp switch C205-6, circuit CLF23 (WH/VT), harness side and headlamp switch C205-3, circuit GD133 (BK), harness side.
- Is the voltage greater than 5 volts?
Yes
INSTALL a new headlamp switch. REFER to Headlamp Switch Service and Repair. TEST the system for normal operation.
No
REPAIR circuit GD133 (BK) for an open. TEST the system for normal operation.
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C7 CHECK THE HEADLAMP SWITCH INPUT CIRCUITS FOR A SHORT TO GROUND
- Disconnect: SCCM C2414A.
- Measure the resistance between the headlamp switch, harness side and ground as follows:
- Are the resistances greater than 10,000 ohms?
Yes
GO to C8.
No
REPAIR the circuit in question for a short to ground. TEST the system for normal operation.
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C8 CHECK THE HEADLAMP SWITCH INPUT CIRCUITS FOR AN OPEN
- Measure the resistance between the headlamp switch, harness side and the SCCM, harness side as follows:
- Are the resistances less than 5 ohms?
Yes
GO to C10.
No
REPAIR the circuit in question for an open. TEST the system for normal operation.
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C9 CHECK THE BCM OUTPUT
- Ignition OFF.
- Disconnect: BCM C2280E.
- Ignition ON.
- Does the LH or RH headlamp continue to illuminate?
Yes
REPAIR circuit CLF04 (BN/BU) (LH headlamp) or circuit CLF05 (BU/GN) (RH headlamp) for a short to voltage as necessary. TEST the system for normal operation.
No
GO to C11.
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C10 CHECK FOR CORRECT SCCM OPERATION
- Disconnect all the SCCM connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the SCCM connectors and make sure they seat correctly.
- Operate the system and verify the concern is still present.
- Is the concern still present?
Yes
INSTALL a new SCCM. REFER to Steering Column Switches Service and Repair. TEST the system for normal operation.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
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C11 CHECK FOR CORRECT BCM OPERATION
- Disconnect all the BCM connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the BCM connectors and make sure they seat correctly.
- Operate the system and verify the concern is still present.
- Is the concern still present?
Yes
INSTALL a new BCM. REFER to Multifunction Electronic Modules Service and Repair. TEST the system for normal operation.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
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