Pinpoint Test C: The Low Beams Are Always On
Headlamps
Pinpoint Test C: The Low Beams Are Always On
Refer to Wiring Diagram Set 85, Headlamps for schematic and connector information Electrical Diagrams.
Normal Operation
The Body Control Module (BCM) 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 BCM (Body Control Module). When the BCM (Body Control Module) detects the headlamp switch in the HEADLAMPS ON position, the BCM (Body Control Module) provides ground for the low beam relay coil. When the low beam relay energizes, voltage is routed through Battery Junction Box (BJB) fuses 35 (10A) (LH low beam) and 36 (10A) (RH low beam) to the headlamps.
If the BCM (Body Control Module) detects multiple or no active headlamp switch inputs, the BCM (Body Control Module) defaults the exterior lamps on.
Vehicles equipped with Daytime Running Lamps (DRL) utilize a separate relay in conjunction with the existing headlamp circuitry to illuminate the low beams at a reduced intensity when the ignition is in RUN.
- DTC B10A6:92 (Main Light Switch: Performance Or Incorrect Operation)- a continuous and on-demand DTC that sets when the BCM (Body Control Module) detects a no inputs from the headlamp switch are active (circuits open) or more than one headlamp switch input circuits are active (short to ground).
- DTC B10A8:14 (Low Beam Relay: Circuit Short To Ground Or Open)- a continuous and on-demand DTC that sets when the BCM (Body Control Module) detects a short to ground from the low beam relay coil ground controlled circuit.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Low beam relay
- DRL (Daytime Running Lamps) system concern
- Headlamp switch
- BCM (Body Control Module)
PINPOINT TEST C : THE LOW BEAMS 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 BCM (Body Control Module) HEADLAMP SWITCH PIDs
NOTE: Make sure the headlamp switch is aligned in the correct position when monitoring the PIDs.
NOTE: Only one PID should indicate ON at each headlamp switch position.
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: BCM (Body Control Module) DataLogger.
- While moving the headlamp switch through all positions (OFF, PARKING LAMPS and HEADLAMPS), monitor the BCM (Body Control Module) headlamp switch input PIDs (LIGHTNG_MODE, PARK_LMP_SW, LOW_BEAM_SW).
Do the headlamp switch positions agree with the PIDs (with only one PID indicating ON in each position?
Yes
GO to C7.
No
GO to C2.
C2 CHECK THE HEADLAMP SWITCH
- Ignition OFF.
- Disconnect: Headlamp Switch C205.
- Carry out the headlamp switch component test.
Does the headlamp switch pass the component test?
Yes
GO to C3.
No
INSTALL a new headlamp switch. REFER to Headlamp Switch Service and Repair. CLEAR the DTCs. TEST the system for normal operation.
C3 DETERMINE IF A HEADLAMP SWITCH INPUT IS SHORT TO GROUND
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: BCM (Body Control Module) DataLogger.
- Monitor the BCM (Body Control Module) headlamp switch input PIDs (LIGHTNG_MODE, PARK_LMP_SW, LOW_BEAM_SW).
Do any of the headlamp switch PIDs indicate ON?
Yes
GO to C4.
No
GO to C5.
C4 CHECK THE HEADLAMP SWITCH INPUT CIRCUITS FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: BCM (Body Control Module) C2280E.
- Measure the resistance between the headlamp switch, harness side and ground as follows:
Headlamp Switch Connector-Pin Circuit C205-6 CLF23 (WH/VT) C205-2 CLF24 (YE/BU) C205-7 CLF18 (BU/WH)
Are the resistances greater than 10,000 ohms?
Yes
GO to C12.
No
REPAIR the circuit in question for a short to ground. CLEAR the DTCs. TEST the system for normal operation.
C5 DETERMINE IF A HEADLAMP SWITCH INPUT IS OPEN
- Enter the following diagnostic mode on the scan tool: BCM (Body Control Module) DataLogger.
- Monitor the BCM (Body Control Module) headlamp switch input PIDs while connecting a fused jumper wire between the headlamp switch pins and ground as follows:
PID to Monitor Headlamp Switch Connector-Pin Circuit LIGHTNG_MODE C205-6 CLF23 (WH/VT) PARK_LMP_SW C205-2 CLF24 (YE/BU) LOW_BEAM_SW C205-7 CLF18 (BU/WH)
Do the PIDs indicate ON with each corresponding connection?
Yes
REPAIR circuit GD115 (BK/GY) for an open. CLEAR the DTCs. TEST the system for normal operation.
No
GO to C6.
C6 CHECK THE HEADLAMP SWITCH INPUT CIRCUITS FOR AN OPEN
- Ignition OFF.
- Disconnect: BCM (Body Control Module) C2280E.
- Measure the resistance between the headlamp switch, harness side and the BCM (Body Control Module), harness side as follows:
Headlamp Switch Connector-Pin BCM (Body Control Module) Connector-Pin Circuit C205-6 C2280E-3 CLF23 (WH/VT) C205-2 C2280E-9 CLF24 (YE/BU) C205-7 C2280E-13 CLF18 (BU/WH)
Are the resistances less than 5 ohms?
Yes
GO to C12.
No
REPAIR the circuit in question for an open. CLEAR the DTCs. TEST the system for normal operation.
C7 CHECK THE LOW BEAM RELAY OUTPUT
- Ignition OFF.
- Disconnect: Low Beam Relay.
- Ignition ON.
Do the low beams continue to illuminate?
Yes
GO to C8.
No
If equipped with DRL (Daytime Running Lamps), GO to C9.
If not equipped with DRL (Daytime Running Lamps), GO to C10.
C8 ISOLATE THE SHORT TO VOLTAGE
- Disconnect: BJB (Battery Junction Box) Fuses 35 (10A) and 36 (10A).
Does either low beam continue to illuminate?
Yes
REPAIR circuit CBB35 (YE/GY) (LH headlamp) or circuit CBB36 (BU/BN) (RH headlamp) for a short to voltage as necessary. TEST the system for normal operation.
No
REPAIR circuit CLF09 (BU/GY) for a short to voltage. TEST the system for normal operation.
C9 CHECK THE DRL (Daytime Running Lamps) SYSTEM
- Ignition OFF.
- Measure the voltage between the low beam relay pin 4, circuit CLF13 (YE/BU), BJB (Battery Junction Box) face side and ground.
Is any voltage present?
Yes
GO to Pinpoint Test G Pinpoint Test G: The Daytime Running Lamps (DRL) Are On With The Ignition Off.
No
GO to C10.
C10 CHECK THE LOW BEAM RELAY
- Ignition OFF.
- Substitute a known good relay.
- Ignition ON.
Do the low beams continue to illuminate?
Yes
REMOVE the known good relay. GO to C11.
No
REMOVE the known good relay. INSTALL a new low beam relay. TEST the system for normal operation.
C11 CHECK THE LOW BEAM RELAY COIL GROUND CONTROLLED CIRCUIT FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: BCM (Body Control Module) C2280D.
- Measure the resistance between the low beam relay pin 2, circuit CLF04 (BN/BU), BJB (Battery Junction Box) face side and ground.
Is the resistance greater than 10,000 ohms?
Yes
GO to C12.
No
REPAIR circuit CLF04 (BN/BU), for a short to ground. CLEAR the DTCs. TEST the system for normal operation.
C12 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.