Pinpoint Test B: One Low Beam Headlamp Is Inoperative

Headlamps

Pinpoint Test B: One Low Beam Headlamp Is Inoperative

Normal Operation

When the Smart Junction Box (SJB) detects the headlamp switch in the HEADLAMPS ON position and the multifunction switch in the LOW BEAM position, the SJB (Smart Junction Box) provides voltage to the LH and RH low beams. Each headlamp has its own ground circuit.

This pinpoint test is intended to diagnose the following:

- Fuse

- Wiring, terminals or connectors

- Body builder equipment

- SJB (Smart Junction Box)

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 varying wattage ratings and resulting current draw differences, certain aftermarket headlamp bulbs may cause the SJB (Smart Junction Box) to shut down the short circuit protection, resulting in the low beams becoming inoperative. Verify that the bulbs meet Ford specifications. If the bulbs do not meet Ford specifications, install the correct bulbs. Clear the DTCs and run the self-test (required to reset the SJB (Smart Junction Box) low beam output driver). Correct any unresolved DTCs. Test the system for normal operation.

B1 USE THE RECORDED DTCs FROM THE SJB (Smart Junction Box) SELF-TEST

- Check the recorded results from the SJB (Smart Junction Box) self-test.

Was DTC B2A2E or DTC B2A30 recorded?

Yes
GO to B2.

No
VERIFY the SJB (Smart Junction Box) fuse 7 (10A) (LH low beam) or fuse 8 (10A) (RH low beam) is OK. If OK, GO to B4.

If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short Electrical Diagrams. After the repair:

If no DTCs are present, TEST the system for normal operation.

If DTC B106E is present, CLEAR the DTCs and REPEAT the self-test (required to enable the low beam output driver if DTC B106E is present). TEST the system for normal operation.

If DTC B106F is present, INSTALL a new SJB (Smart Junction Box). TEST the system for normal operation.

B2 CHECK THE SJB (Smart Junction Box) HEADLAMP OUTPUT CIRCUIT FOR VOLTAGE

- Ignition OFF.

- Disconnect: Inoperative Headlamp (Except Stripped Chassis).

- Disconnect: Body Builder C1010 (Stripped Chassis).

- Place the headlamp switch in the HEADLAMPS ON position.

- For vehicles with aerodynamic headlamps, measure the voltage between the LH headlamp C1284-1, circuit CLF04 (BN/BU), harness side and ground; or between the RH headlamp C1285-1, circuit CLF05 (BU/GN), harness side and ground.

- For vehicles with sealed beam headlamps, measure the voltage between the LH headlamp C1021-3, circuit CLF04 (BN/BU), harness side and ground; or between the RH headlamp C1041-3, circuit CLF05 (BU/GN), harness side and ground.

- For stripped chassis vehicles, measure the voltage between the body builder C1010-4 (LH headlamp), circuit CLF04 (BN/BU), harness side and ground; or between the body builder C1010-7 (RH headlamp), circuit CLF05 (BU/GN), harness side and ground.

Is the voltage greater than 10 volts?

Yes
For all except stripped chassis vehicles, REPAIR the ground circuit of the lamp in question for an open. TEST the system for normal operation.

For stripped chassis vehicles, the vehicle is operating correctly. REFER to the body builder manual to continue diagnosis.

No
GO to B3.

B3 CHECK THE SJB (Smart Junction Box) HEADLAMP OUTPUT CIRCUIT FOR AN OPEN

- Place the headlamp switch in the OFF position.

- Disconnect: SJB (Smart Junction Box) C2280E.

- For vehicles with aerodynamic headlamps, measure the resistance between the LH headlamp C1284-1, circuit CLF04 (BN/BU), harness side and the SJB (Smart Junction Box) C2280E-13, circuit CLF04 (BN/BU), harness side; or between the RH headlamp C1285-1, circuit CLF05 (BU/GN), harness side and the SJB (Smart Junction Box) C2280E-4, circuit CLF05 (BU/GN), harness side.

- For vehicles with sealed beam headlamps, measure the resistance between the LH headlamp C1021-3, circuit CLF04 (BN/BU), harness side and the SJB (Smart Junction Box) C2280E-13, circuit CLF04 (BN/BU), harness side; or between the RH headlamp C1041-3, circuit CLF05 (BU/GN), harness side and the SJB (Smart Junction Box) C2280E-4, circuit CLF05 (BU/GN), harness side.

- For stripped chassis vehicles, measure the resistance between the body builder C1010-4 (LH headlamp), circuit CLF04 (BN/BU), harness side and the SJB (Smart Junction Box) C2280E-13, circuit CLF04 (BN/BU), harness side; or between the body builder C1010-7 (RH headlamp), circuit CLF05 (BU/GN), harness side and the SJB (Smart Junction Box) C2280E-4, circuit CLF05 (BU/GN), harness side.

Is the resistance less than 5 ohms?

Yes
GO to B6.

No
REPAIR circuit CLF04 (BN/BU) (LH headlamp) or circuit CLF05 (BU/GN) (RH headlamp) for an open. TEST the system for normal operation.

B4 ISOLATE THE BULB (OR BODY BUILDER EQUIPMENT) AS THE CAUSE OF THE SHORT

- Ignition OFF.

- Disconnect: Inoperative Headlamp (Except Stripped Chassis).

- Disconnect: Body Builder C1010 (Stripped Chassis).

- Ignition ON.

- Enter the following diagnostic mode on the scan tool: SJB (Smart Junction Box) Self-Test.

- Clear the DTCs and repeat the self-test (required to enable the low beam output driver if DTC B106E is present).

- Place the headlamp switch in the HEADLAMPS ON position.

- For vehicles with aerodynamic headlamps, measure the voltage between the LH headlamp C1284-1, circuit CLF04 (BN/BU), harness side and ground; or between the RH headlamp C1285-1, circuit CLF05 (BU/GN), harness side and ground.

Is the voltage greater than 10 volts?

Yes
For all except stripped chassis vehicles, INSTALL a new headlamp bulb. REFER to Headlamp Bulb Service and Repair. TEST the system for normal operation.

For stripped chassis vehicles, the vehicle is operating correctly. REFER to the body builder manual to continue diagnosis of the short to ground.

No
GO to B5.

B5 CHECK THE SJB (Smart Junction Box) LOW BEAM OUTPUT CIRCUIT FOR A SHORT TO GROUND

- Ignition OFF.

- Disconnect: SJB (Smart Junction Box) C2280E.

- For vehicles with aerodynamic headlamps, measure the resistance between the LH headlamp C1284-1, circuit CLF04 (BN/BU), harness side and ground; or between the RH headlamp C1285-1, circuit CLF05 (BU/GN), harness side and ground.

- For vehicles with sealed beam headlamps, measure the resistance between the LH headlamp C1021-3, circuit CLF04 (BN/BU), harness side and ground; or between the RH headlamp C1041-3, circuit CLF05 (BU/GN), harness side and ground.

- For stripped chassis vehicles, measure the resistance between the body builder C1010-4 (LH headlamp), circuit CLF04 (BN/BU), harness side and ground; or between the body builder C1010-7 (RH headlamp), circuit CLF05 (BU/GN), harness side and ground.

Is the resistance greater than 10,000 ohms?

Yes
GO to B6.

No
REPAIR circuit CLF04 (BN/BU) (LH low beam) or circuit CLF05 (BU/GN) (RH low beam) for a short to ground. After the repair:

If no DTCs are present, TEST the system for normal operation.

If DTC B106E is present, CLEAR the DTCs and REPEAT the self-test (required to enable the backlighting output driver if DTC B106E is present). TEST the system for normal operation.

If DTC B106F is present, INSTALL a new SJB (Smart Junction Box). TEST the system for normal operation.

B6 CHECK FOR CORRECT SJB (Smart Junction Box) OPERATION

- Disconnect all the SJB (Smart Junction Box) connectors.

- Check for:
- corrosion

- damaged pins

- pushed-out pins

- Connect all the SJB (Smart Junction Box) 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 (Smart Junction Box). 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.