Pinpoint Test B: One Low Beam Headlamp Is Inoperative
Headlamps
Pinpoint Tests
Pinpoint Test B: One Low Beam Headlamp Is Inoperative
Refer to Wiring Diagram Set 85, Headlamps/Autolamps for schematic and connector information. Diagrams By Number
Normal Operation
The Smart Junction Box (SJB) receives voltage from the Battery Junction Box (BJB) through circuits SBB34 (YE/RD) (LH headlamp) and SBB29 (GY/RD) (RH headlamp). When the SJB detects the headlamp switch in the HEADLAMPS ON position and the multifunction switch in the LOW BEAM position, the SJB provides voltage through circuits CLF04 (BN/BU) (LH headlamp) and CLF05 (BU/GN) (RH headlamp) to the low beam headlamps. Ground is supplied on circuits GD120 (BK/GN) (LH headlamp) and GD123 (BK/GY) (RH headlamp).
- DTC B1797 (Lamp Headlamp Low-Beam Circuit Short to Ground) - a continuous and on-demand DTC that sets when the SJB detects a short to ground (high amperage draw) from the LH or RH low beam voltage supply circuit. The self-test must be run after the repair in order for the SJB to enable the output for the low beam voltage supply.
- DTC B2501 (LF Lamp Low Beam Circuit Failure) - a continuous and on-demand DTC that sets when the SJB detects an open from the LH low beam voltage supply circuit.
- DTC B2503 (RF Lamp Low Beam Circuit Failure) - a continuous and on-demand DTC that sets when the SJB detects an open from the RH low beam voltage supply circuit.
This pinpoint test is intended to diagnose the following:
- Fuse
- Wiring, terminals or connectors
- SJB
PINPOINT TEST B: ONE LOW BEAM HEADLAMP IS INOPERATIVE
NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
NOTE: Due to the varying wattage ratings and resulting current draw of certain aftermarket headlamp bulbs, the SJB may activate its short circuit protection strategy, resulting in the low beam output circuit becoming inoperative. Make sure that the bulbs meet Ford specifications. If the bulbs do not meet Ford specifications, install the correct bulbs. Run the on-demand self-test (required to clear certain DTCs and reset the SJB). Correct any unresolved DTCs. Clear all DTCs. Test the system for normal operation.
NOTE: Failure to disconnect the battery when instructed will result in false resistance readings. Refer to Battery.
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B1 CHECK THE RECORDED DTCs FROM THE SJB SELF-TEST
- Check the recorded DTCs from the SJB self-test.
- Is DTC B1797 recorded?
Yes
GO to B6.
No
GO to B2.
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B2 CHECK THE HIGH BEAM OPERATION
- Ignition ON.
- Place the headlamp switch in the HEADLAMPS ON position.
- Place the multifunction switch in the HIGH BEAM position and observe the headlamp in question.
- Does the high beam in the headlamp in question illuminate?
Yes
GO to B5.
No
TURN the headlamps off. GO to B3.
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B3 CHECK CIRCUIT SBB34 (YE/RD) (LH HEADLAMP) OR CIRCUIT SBB29 (GY/RD) (RH HEADLAMP) FOR AN OPEN
- Ignition OFF.
- Disconnect: SJB C2280e.
- Measure the voltage between the SJB C2280e-2 (LH headlamp), circuit SBB34 (YE/RD), harness side and ground; or between the SJB C2280e-31 (RH headlamp), circuit SBB29 (GY/RD), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to B4.
No
VERIFY the BJB fuse 34 (20A) or fuse 29 (20A) is OK. If OK, REPAIR the circuit in question. CLEAR the DTCs. REPEAT the self-test. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short.
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B4 CHECK CIRCUIT GD120 (BK/GN) (LH HEADLAMP) OR CIRCUIT GD123 (BK/GY) (RH HEADLAMP) FOR AN OPEN
- Disconnect: Negative Battery Cable.
- Disconnect: Inoperative Headlamp.
- Measure the resistance between the LH headlamp C1284-2 or C1021-2, circuit GD120 (BK/GN), harness side and ground; or between the RH headlamp C1285-2 or C1041-2, circuit GD123 (BK/GY), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
GO to B7.
No
REPAIR the circuit in question. CLEAR the DTCs. REPEAT the self-test.
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B5 CHECK CIRCUIT CLF04 (BN/BU) (LH HEADLAMP) OR CIRCUIT CLF05 (BU/GN) (RH HEADLAMP) FOR AN OPEN
- Ignition OFF.
- Disconnect: Inoperative Headlamp.
- Disconnect: SJB C2280e.
- If the LH low beam is inoperative, measure the resistance between the LH headlamp C1284-1 or C1021-3, circuit CLF04 (BN/BU), harness side and the SJB C2280e-3, circuit CLF04 (BN/BU), harness side.
- If the RH low beam is inoperative, measure the resistance between the RH headlamp C1285-1 or C1041-3, circuit CLF05 (BU/GN), harness side and the SJB C2280e-20, circuit CLF05 (BU/GN), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to B7.
No
REPAIR the circuit in question. CLEAR any DTCs. REPEAT the self-test.
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B6 CHECK CIRCUIT CLF04 (BN/BU) (LH HEADLAMP) OR CIRCUIT CLF05 (BU/GN) (RH HEADLAMP) FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: Inoperative Headlamp.
- Disconnect: SJB C2280e.
- Measure the resistance between the inoperative headlamp, harness side and ground as follows:
- Is the resistance greater than 10,000 ohms?
Yes
GO to B7.
No
REPAIR the circuit in question. RUN the on-demand self-test (required to clear certain DTCs). CORRECT any unresolved DTCs. CLEAR all DTCs. TEST the system for normal operation.
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B7 CHECK FOR CORRECT SJB OPERATION
- Disconnect all the SJB connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the SJB 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 SJB. 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. CLEAR the DTCs. REPEAT the self-test.
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