Pinpoint Test B: One Low Beam Headlamp Is Inoperative
Headlamps
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 Lighting Control Module (LCM) is supplied voltage from the Central Junction Box (CJB) for the LH and RH low beams or ballasts (vehicles equipped with High Intensity Discharge (HID) headlamps).
When a request for the low beams is received by the LCM, the LCM provides voltage to the LH and RH headlamps.
The ballast provides the high voltage necessary for the HID bulbs to illuminate.
This pinpoint test is intended to diagnose the following:
- Fuse
- Wiring, terminals or connectors
- HID bulb
- Ballast
- LCM
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.
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B1 CHECK FOR VOLTAGE TO THE HEADLAMP
- Ignition OFF.
- Disconnect: Inoperative Headlamp.
- Place the headlamp switch in the HEADLAMPS ON position.
- Measure the voltage between the inoperative headlamp, harness side and ground as follows:
- Is the voltage greater than 10 volts?
Yes
For vehicles with halogen headlamps, REPAIR circuit 57 (BK) for an open. TEST the system for normal operation.
For vehicles with HID headlamps, GO to B2.
No
GO to B4.
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B2 CHECK FOR VOLTAGE TO THE HEADLAMP USING THE CONNECTOR GROUND
- Measure the voltage between the LH headlamp C1353-C, circuit 161 (DG/OG), harness side and the LH headlamp C1353-B, circuit 57 (BK), harness side; or between the RH headlamp C1354-C, circuit 161 (DG/OG), harness side and the RH headlamp C1354-B, circuit 57 (BK), harness side
- Is the voltage greater than 10 volts?
Yes
GO to B3.
No
REPAIR circuit 57 (BK) for an open. TEST the system for normal operation.
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B3 CHECK THE BALLAST
- Place the headlamp switch in the OFF position.
- Install a known good ballast.
- Place the headlamp switch in the HEADLAMPS ON position.
- Does the headlamp illuminate?
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.
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B4 CHECK FOR VOLTAGE TO THE LCM
- Place the headlamp switch in the OFF position.
- Disconnect: LCM C2145d (LH Headlamp) or C2145c (RH Headlamp).
- Measure the voltage between the LCM C2145d-21 (LH low beam), circuit 1055 (WH/LG), harness side and ground; or between the LCM C2145c-19 (RH low beam), circuit 1056 (DB/LG), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to B5.
No
VERIFY the CJB fuse 20 (10A) or fuse 22 (10A) 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
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B5 CHECK THE HEADLAMP VOLTAGE SUPPLY CIRCUIT FOR AN OPEN
- Measure the resistance between the inoperative headlamp, harness side and the LCM, harness side as follows:
- Is the resistance less than 5 ohms?
Yes
GO to B6.
No
REPAIR circuit 161 (DG/OG) for an open. TEST the system for normal operation.
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B6 CHECK THE HEADLAMP VOLTAGE SUPPLY CIRCUIT FOR A SHORT TO GROUND
- 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 for a short to ground. TEST the system for normal operation.
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B7 CHECK FOR CORRECT LCM OPERATION
- Disconnect all the LCM connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the LCM 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 LCM. REFER to Multifunction Electronic Modules Lighting Control Module (LCM). 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.
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