Pinpoint Test A: One Or Both Low Beams Are Inoperative
Headlamps
Pinpoint Test A: One Or Both Low Beams Are Inoperative
Refer to Wiring Diagram Set 85, Headlamps for schematic and connector information Electrical Diagrams.
Normal Operation
The low beams do not turn on unless the ignition is in RUN. The Body Control Module (BCM) monitors a circuit that is provided voltage when the ignition is in RUN.
Voltage is provided at all times to the switch and coil sides of the low beam relay. 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.
- DTC B10A8:12 (Low Beam Relay: Circuit Short To Battery)- a continuous and on-demand DTC that sets when the BCM (Body Control Module) detects a short to voltage from the low beam relay coil ground controlled circuit.
- 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 an open from the low beam relay coil ground controlled circuit.
This pinpoint test is intended to diagnose the following:
- Fuse
- Wiring, terminals or connectors
- Low beam relay
- Headlamp assembly
- BCM (Body Control Module)
PINPOINT TEST A : ONE OR BOTH LOW BEAMS ARE INOPERATIVE
NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
A1 DETERMINE IF BOTH HEADLAMPS ARE INOPERATIVE
- Ignition ON.
- Place the headlamp switch in the HEADLAMPS ON position and observe the headlamps.
Are both headlamps inoperative?
Yes
VERIFY the BJB (Battery Junction Box) fuses 19 (20A) and 21 (7.5A) are OK. If OK, GO to A5. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short Electrical Diagrams.
No
VERIFY the BJB (Battery Junction Box) fuse 35 (10A) (LH low beam) or fuse 36 (10A) (RH low beam) is OK. If OK, GO to A2. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short Electrical Diagrams.
A2 CHECK FOR VOLTAGE TO THE HEADLAMP
- Place the headlamp switch in the HEADLAMPS OFF position.
- Ignition OFF.
- Disconnect: Inoperative Headlamp.
- Ignition ON.
- Place the headlamp switch in the HEADLAMPS ON position.
- Measure the voltage between the LH headlamp C1021-1, circuit CBB35 (YE/GY), harness side and ground; or between the RH headlamp C1041-1, circuit CBB36 (BU/BN), harness side and ground.
Is the voltage greater than 10 volts?
Yes
GO to A3.
No
GO to A4.
A3 CHECK THE HEADLAMP GROUND CIRCUIT FOR AN OPEN
- Measure the voltage between the LH headlamp C1021-1, circuit CBB35 (YE/GY), harness side and the LH headlamp C1021-2, circuit GD123 (BK/GY), harness side; or between the RH headlamp C1041-1, circuit CBB36 (BU/BN), harness side and the RH headlamp C1041-2, circuit GD188 (BK/YE), harness side.
Is the voltage greater than 10 volts?
Yes
REPAIR or INSTALL a new headlamp assembly. REFER to Headlamp Assembly Service and Repair. TEST the system for normal operation.
No
REPAIR circuit GD123 (BK/GY) (LH headlamp) or circuit GD188 (BK/YE) (RH headlamp) for an open. TEST the system for normal operation.
A4 CHECK FOR VOLTAGE TO THE LOW BEAM FUSE
- Disconnect: BJB (Battery Junction Box) Fuse 35 (10A) (LH low beam) or Fuse 36 (10A) (RH low beam).
- Measure the voltage between the BJB (Battery Junction Box) fuse 35 (10A) (LH low beam), circuit CLF09 (BU/GY), input side and ground; or between the BJB (Battery Junction Box) fuse 36 (10A) (RH low beam), circuit CLF09 (BU/GY), input side and ground.
Is the voltage greater than 10 volts?
Yes
REPAIR circuit CBB35 (YE/GY) (LH headlamp) or circuit CBB36 (BU/BN) (RH headlamp) for an open. TEST the system for normal operation.
No
REPAIR circuit CLF09 (BU/GY) for an open. TEST the system for normal operation.
A5 CHECK THE LOW BEAM RELAY
- Place the headlamp switch in the HEADLAMPS OFF position.
- Ignition OFF.
- Disconnect: Low Beam Relay.
- Substitute a known good relay.
- Ignition ON.
- Place the headlamp switch in the HEADLAMPS ON position.
Do the headlamps illuminate?
Yes
REMOVE the known good relay. INSTALL a new low beam relay. TEST the system for normal operation.
No
REMOVE the known good relay. GO to A6.
A6 CHECK FOR VOLTAGE TO THE LOW BEAM RELAY
- Ignition OFF.
- Measure the voltage between the low beam relay pin 5, circuit SBB19 (BU/RD), BJB (Battery Junction Box) face side and ground.
Is the voltage greater than 10 volts?
Yes
GO to A7.
No
REPAIR circuit SBB19 (BU/RD) for an open. TEST the system for normal operation.
A7 BYPASS THE LOW BEAM RELAY
- Connect a fused jumper wire between the low beam relay pin 5, circuit SBB19 (BU/RD), BJB (Battery Junction Box) face side and the low beam relay pin 3, circuit CLF09 (BU/GY), BJB (Battery Junction Box) face side.
Do the headlamps illuminate?
Yes
REMOVE the jumper wire. GO to A8.
No
REMOVE the jumper wire. REPAIR circuit CLF09 (BU/GY) for an open. TEST the system for normal operation.
A8 CHECK FOR VOLTAGE TO THE LOW BEAM RELAY COIL
- Measure the voltage between the low beam relay pin 1, circuit SBB21 (GY/RD), BJB (Battery Junction Box) face side and ground.
Is the voltage greater than 10 volts?
Yes
GO to A9.
No
REPAIR circuit SBB21 (GY/RD) for an open. CLEAR the DTCs. TEST the system for normal operation.
A9 CHECK THE LOW BEAM RELAY COIL GROUND CONTROLLED CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: BCM (Body Control Module) C2280D.
- Ignition ON.
- Measure the voltage between the BCM (Body Control Module) C2280D-5, circuit CLF04 (BN/BU), harness side and ground.
Is any voltage present?
Yes
REPAIR circuit CLF04 (BN/BU) for a short to voltage. CYCLE the ignition ON then OFF. CLEAR the DTCs. TEST the system for normal operation.
No
GO to A10.
A10 CHECK THE LOW BEAM RELAY COIL GROUND CONTROLLED CIRCUIT FOR AN OPEN
- Ignition OFF.
- Connect: Low Beam Relay.
- Ignition ON.
- Measure the voltage between the BCM (Body Control Module) C2280D-5, circuit CLF04 (BN/BU), harness side and ground.
Is the voltage greater than 10 volts?
Yes
GO to A11.
No
REPAIR circuit CLF04 (BN/BU) for an open. CLEAR the DTCs. TEST the system for normal operation.
A11 CHECK THE IGNITION RUN INPUT CIRCUIT FOR AN OPEN
- Disconnect: BCM (Body Control Module) C2280B.
- Ignition ON.
- Measure the voltage between the BCM (Body Control Module) C2280B-4, circuit CBP21 (BU/GY), harness side and ground.
Is the voltage greater than 10 volts?
Yes
GO to A12.
No
REPAIR circuit CBP21 (BU/GY) for an open. CLEAR the DTCs. TEST the system for normal operation.
A12 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.