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

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 provides voltage to the LH and RH low beam headlamps.

Vehicles equipped with High Intensity Discharge (HID) headlamps utilize a second (hot at all times) voltage feed to the ballasts from the Battery Junction Box (BJB).

When the ballasts receive the headlamp on voltage from the SJB, the ballasts provide high voltage to the HID bulbs.

This pinpoint test is intended to diagnose the following:

- Fuse
- Wiring, terminals or connectors
- Ballast
- HID bulb
- Headlamp assembly ( HID only)
- 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.

-------------------------------------------------
B1 CHECK FOR SJB SUPPLIED VOLTAGE TO THE HEADLAMP

- Ignition OFF.
- Disconnect: Inoperative Headlamp.
- Place the headlamp switch in the HEADLAMPS ON position.
- For vehicles with halogen headlamps, measure the voltage between the LH headlamp C1284b-1, circuit CLF04 (BN/BU), harness side and ground; or between the RH headlamp C1285b-1, circuit CLF05 (BU/GN), harness side and ground.

- For vehicles with HID headlamps, measure the voltage between the LH headlamp C1284a-2, circuit CLF04 (BN/BU), harness side and ground; or between the RH headlamp C1285a-2, circuit CLF05 (BK/GN), harness side and ground.

- Is the voltage greater than 10 volts?

Yes
For vehicles with halogen headlamps, REPAIR circuit GD123 (BK/GY) (LH headlamp) or circuit GD120 (BK/GN) (RH headlamp) for an open. CLEAR the DTCs. REPEAT the self-test.

For vehicles with HID headlamps, GO to B6.

No
VERIFY the SJB fuse 7 (10A) (LH low beam) or fuse 8 (10A) (RH low beam) is OK. If OK, GO to B2. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short. Diagrams By Number

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. REFER to Multifunction Electronic Modules Service and Repair. TEST the system for normal operation.

-------------------------------------------------
B2 REPEAT THE SJB SELF-TEST AND CHECK FOR VOLTAGE TO THE HEADLAMP

- Place the headlamp switch in the OFF position.
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: SJB Self-Test.
- Clear the DTCs and repeat the on-demand 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 halogen headlamps, measure the voltage between the LH headlamp C1284b-1, circuit CLF04 (BN/BU), harness side and ground; or between the RH headlamp C1285b-1, circuit CLF05 (BU/GN), harness side and ground.

- Is the voltage greater than 10 volts?

Yes
For vehicle with halogen headlamps, INSTALL a new headlamp bulb. REFER to Headlamp Bulb Service and Repair. TEST the system for normal operation.

For vehicles with HID headlamps, GO to B5.

No
GO to B3.

-------------------------------------------------
B3 CHECK THE SJB LOW BEAM OUTPUT CIRCUIT FOR A SHORT TO GROUND

- Ignition OFF.
- Disconnect: SJB C2280e.
- For vehicles with halogen headlamps, measure the resistance between the LH headlamp C1284b-1, circuit CLF04 (BN/BU), harness side and ground; or between the RH headlamp C1285b-1, circuit CLF05 (BU/GN), harness side and ground.

- For vehicles with HID headlamps, measure the resistance between the LH headlamp C1284a-2, circuit CLF04 (BN/BU), harness side and ground; or between the RH headlamp C1285a-2, circuit CLF05 (BU/GN), harness side and ground.

- Is the resistance greater than 10,000 ohms?

Yes
GO to B4.

No
REPAIR circuit CLF04 (BN/BU) (LH headlamp) or circuit CLF05 (BU/GN) (RH headlamp) for a short to ground.

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 B106E is present, INSTALL a new SJB. REFER to Multifunction Electronic Modules Service and Repair. TEST the system for normal operation.

-------------------------------------------------
B4 CHECK THE SJB LOW BEAM OUTPUT CIRCUIT FOR AN OPEN

- Measure the resistance between the inoperative headlamp, harness side and the SJB as follows:

- Is the resistance less than 5 ohms?

Yes
GO to B10.

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

-------------------------------------------------
B5 CHECK THE HEADLAMP HARNESS FOR A SHORT

- Inspect the headlamp harness for shorts.
- Is the headlamp harness OK?

Yes
INSTALL a new ballast. REFER to Ballast Service and Repair. TEST the system for normal operation.

No
REPAIR or INSTALL a new headlamp assembly. REFER to Headlamp Assembly Service and Repair. TEST the system for normal operation.

-------------------------------------------------
B6 CHECK FOR HOT AT ALL TIMES VOLTAGE TO THE HEADLAMP

- Place the headlamp switch in the OFF position.
- Measure the voltage between the LH headlamp C1284a-3, circuit SBB13 (GY/RD), harness side and ground; or between the RH headlamp C1285a-3, circuit SBB16 (VT/RD), harness side and ground.

- Is the voltage greater than 10 volts?

Yes
GO to B7.

No
VERIFY the BJB fuse 13 (20A) (LH headlamp) or fuse 16 (20A) (RH headlamp) is OK. If OK, REPAIR the circuit in question for an open. TEST the system for normal operation. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short. Diagrams By Number

-------------------------------------------------
B7 CHECK THE HEADLAMP GROUND CIRCUIT FOR AN OPEN

- Measure the voltage between the LH headlamp C1284a-3, circuit SBB13 (GY/RD), harness side and the LH headlamp C1284a-6, circuit GD120 (BK/GN), harness side; or between the RH headlamp C1285a-3, circuit SBB16 (VT/RD), harness side and the RH headlamp C1285a-6, circuit GD123 (BK/GY), harness side.

- Is the voltage greater than 10 volts?

Yes
GO to B8.

No
REPAIR circuit GD120 (BK/GN) (LH headlamp) or circuit GD123 (BK/GY) (RH headlamp) for an open. TEST the system for normal operation.

-------------------------------------------------
B8 CHECK THE HEADLAMP HARNESS

- Inspect the headlamp harness for opens.
- Is the headlamp harness OK?

Yes
GO to B9.

No
REPAIR or INSTALL a new headlamp assembly. REFER to Headlamp Assembly Service and Repair. TEST the system for normal operation.

-------------------------------------------------
B9 CHECK THE BALLAST

- Substitute a known good ballast and recheck the headlamp operation.
- Does the headlamp operate correctly?

Yes
INSTALL a new ballast. REFER to Ballast Service and Repair. TEST the system for normal operation.

No
INSTALL a new HID bulb. REFER to Headlamp Bulb Service and Repair. TEST the system for normal operation.

-------------------------------------------------
B10 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. REFER to Multifunction Electronic Modules Service and Repair. 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.

-------------------------------------------------