Pinpoint Test B: One Low Beam Headlamp Is Inoperative

WARNING: This page is about a different car, the 2008 Mercury Mariner and 2008 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.

CAUTION: 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 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. 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: Make sure the headlamp bulb is good before continuing diagnostics.

B1 USE THE RECORDED DTCs FROM THE SJB SELF-TEST
- Check the recorded results from the SJB self-test.
- Were any DTCs recorded?
1. YES : For DTC B2A2E or B2A30, go to B2.
  For DTC B2A2F or B2A31, go to B4.
  
  For all other DTCs, REFER to DTC Charts .
2. NO : Go to B5.
B2 CHECK THE SJB HEADLAMP VOLTAGE SUPPLY CIRCUIT FOR VOLTAGE
- Key in OFF position.
- Disconnect: Inoperative Headlamp
- Place the headlamp switch in the HEADLAMPS ON position.
- Measure the voltage between the LH headlamp C1021-1, circuit CLF04 (BN/BU), harness side and ground; or between the RH headlamp C1041-1, circuit CLF05 (BU/GN), harness side and ground.
- Is the voltage greater than 10 volts?
1. YES : REPAIR circuit GD120 (BK/GN) for an open. CLEAR the DTCs. REPEAT the self-test.
2. NO : VERIFY the SJB fuse 7 (10A) (LH low beam) or fuse 8 (10A) is OK. If OK, go to B3.
B3 CHECK THE SJB HEADLAMP VOLTAGE SUPPLY CIRCUIT FOR AN OPEN
- Place the headlamp switch in the OFF position.
- Disconnect: SJB C2280e
- Measure the resistance between the LH headlamp C1021-1, circuit CLF04 (BN/BU), harness side and the SJB C2280e-13, circuit CLF04 (BN/BU), harness side; or between the RH headlamp C1041-1, circuit CLF05 (BU/GN), harness side and the SJB C2280e-4, circuit CLF05 (BU/GN), harness side.
- Is the resistance less than 5 ohms?
1. YES : Go to B5.
2. NO : REPAIR the circuit in question. CLEAR the DTCs. REPEAT the self-test.
B4 CHECK CIRCUIT CLF04 (BN/BU) (LH HEADLAMP) OR CIRCUIT CLF05 (BU/GN) (RH HEADLAMP) FOR A SHORT TO GROUND
- Key in OFF position.
- Disconnect: SJB C2280e
- Disconnect: Inoperative Headlamp
- Measure the resistance between the LH headlamp C1021-1, circuit CLF04 (BN/BU), harness side and ground; or between the RH headlamp C1041-1, circuit CLF05 (BU/GN), harness side and ground.
- Is the resistance greater than 10,000 ohms?
1. YES : Go to B5 .
2. 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.
B5 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?
1. YES : INSTALL a new SJB. REFER to MULTIFUNCTION ELECTRONIC MODULES article. TEST the system for normal operation.
2. 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.