Pinpoint Test C: The Low Beam(s) Are Always On
Headlamps
Pinpoint Test C: The Low Beam(s) Are Always On
Refer to Wiring Diagram Set 85, Headlamps/Autolamps for schematic and connector information Electrical Diagrams.
Normal Operation
The Front Lighting Control Module (FLM) sends a message over the High Speed Controller Area Network (HS-CAN) to the BCM (Body Control Module) to indicate the headlamp switch position. When the BCM (Body Control Module) receives input indicating a request to turn the headlamps on, the BCM (Body Control Module) provides voltage to the LH and RH low beams.
If the BCM (Body Control Module) receives a message from the FLM (Front Lighting Control Module) indicating a fault with the headlamp switch or the BCM (Body Control Module) loses communication with the FLM (Front Lighting Control Module), the BCM (Body Control Module) defaults all the exterior lamps on.
On vehicles with High Intensity Discharge (HID) headlamps, the ballasts are supplied voltage at all times from the Battery Junction Box (BJB). When the ballasts receive a voltage signal from the BCM (Body Control Module), the ballasts provide high voltage to the HID (High Intensity Discharge) bulbs.
- DTC B1D00:15 (Left Low Beam: Circuit Short To Battery or Open)- a DTC that sets when the BCM (Body Control Module) detects a short to voltage from the LH low beam output circuit.
- DTC B1D01:15 (Right Low Beam: Circuit Short To Battery or Open)- a DTC that sets when the BCM (Body Control Module) detects a short to voltage from the RH low beam output circuit.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Headlamp switch (integrated into the FLM (Front Lighting Control Module))
- Headlamp assembly
- BCM (Body Control Module)
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.
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 FLM (Front Lighting Control Module) pass the network test?
Yes
GO to C2.
No
REFER to Information Bus.
C2 CHECK FOR LIGHT SENSOR DTCs
- Review the DTCs recorded from the BCM (Body Control Module) self-test.
Is DTC B1A85:11 or DTC B1A85:13 present?
Yes
GO to Pinpoint Test O Pinpoint Test O: The Autolamps Are On Continuously.
No
GO to C3.
C3 CHECK THE FLM (Front Lighting Control Module) 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: FLM (Front Lighting Control Module) DataLogger.
- While moving the headlamp switch through all positions, monitor the FLM (Front Lighting Control Module) headlamp switch input PID (LT_SW).
Do the headlamp switch positions agree with the PID?
Yes
GO to C4.
No
INSTALL a new FLM (Front Lighting Control Module). REFER to Front Lighting Control Module (FLM) . TEST the system for normal operation.
C4 CHECK THE BCM (Body Control Module) OUTPUT
- Ignition OFF.
- Disconnect: BCM (Body Control Module) C2280E.
- Ignition ON.
Does the LH or RH headlamp continue to illuminate?
Yes
For vehicles with halogen headlamps, REPAIR circuit CLF04 (BN/BU) (LH headlamp) or circuit CLF05 (BN/GN) (RH headlamp) for a short to voltage as necessary. TEST the system for normal operation.
For vehicles with halogen headlamps, GO to C5.
No
GO to C6.
C5 CHECK FOR VOLTAGE TO THE HEADLAMP ASSEMBLY
- Ignition OFF.
- Disconnect: Always On Headlamp.
- Ignition ON.
- Measure the voltage between the LH headlamp C1021A-2, circuit CLF04 (BN/BU), harness side and ground; or between the RH headlamp C1041A-2, circuit CLF05 (BN/GN), harness side and ground.
Is any voltage present?
Yes
REPAIR circuit CLF04 (BN/BU) (LH headlamp) or circuit CLF05 (BN/GN) (RH headlamp) for a short to voltage as necessary. TEST the system for normal operation.
No
REPAIR or install a new headlamp assembly. REFER to Headlamp Assembly . TEST the system for normal operation.
C6 CHECK FOR CORRECT BCM (Body Control Module) OPERATION
- Disconnect all the BCM (Body Control Module) connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the BCM (Body Control Module) 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 (Body Control Module). 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.