Pinpoint Test A: Both Low Beams Are Inoperative
Headlamps
Pinpoint Tests
Pinpoint Test A: Both Low Beams Are Inoperative
Refer to Wiring Diagram Set 85, Headlamps for schematic and connector information. Diagrams By Number
Normal Operation
Voltage is provided at all times to the low beam relay switch side from 2 sources (the low beam interrupt relay and the high beam relay when neither are energized).
The headlamp switch is supplied voltage from the Central Junction Box (CJB) fuse 158 (10A) when the ignition switch is in the RUN position. When the headlamp switch is placed in the HEADLAMPS ON position, voltage is provided to the low beam relay coil to energize the low beam relay. When the low beam relay is energized, voltage is provided through the Battery Junction Box (BJB) fuses 25 (10A) and 23 (10A) to the headlamps.
This pinpoint test is intended to diagnose the following:
- Fuse
- Wiring, terminals or connectors
- Low beam relay
- Headlamp switch
PINPOINT TEST A: BOTH LOW BEAMS ARE 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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A1 CHECK THE LOW BEAM RELAY
- Ignition OFF.
- Disconnect: Low Beam Relay.
- Substitute a known good relay.
- Ignition ON.
- Place the headlamp switch in the HEADLAMPS ON position
- Do the headlamps illuminate?
Yes
REMOVE the known good relay. INSTALL a new low beam relay. TEST the system for normal operation.
No
REMOVE the known good relay. GO to A2.
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A2 CHECK FOR VOLTAGE TO THE LOW BEAM RELAY SWITCH SIDE
- Place the headlamp switch in the OFF position
- Ignition OFF.
- Measure the voltage between the low beam relay pin 3, circuit 30-LE20 (RD), BJB face side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to A3.
No
VERIFY the BJB fuses 8 (15A) and 18 (20A) are OK. If OK, REPAIR circuit 30-LE20 (RD) 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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A3 BYPASS THE LOW BEAM RELAY
- Connect a fused jumper wire between the low beam relay pin 3, circuit 30-LE20 (RD), BJB face side and the low beam relay pin 5, circuit 30-LE1 (RD), BJB face side.
- Do the headlamps illuminate?
Yes
REMOVE the jumper wire. GO to A4.
No
REMOVE the jumper wire. REPAIR circuit 30-LE1 (RD) for an open. TEST the system for normal operation.
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A4 CHECK FOR VOLTAGE TO THE LOW BEAM RELAY COIL
- Ignition ON.
- Place the headlamp switch in the HEADLAMPS ON position
- Measure the voltage between the low beam relay pin 1, circuit 15S-LE19 (GN/BU), BJB face side and ground.
- Is the voltage greater than 10 volts?
Yes
REPAIR the low beam relay ground circuit for an open. TEST the system for normal operation.
No
GO to A5.
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A5 CHECK FOR VOLTAGE TO THE HEADLAMP SWITCH
- Ignition OFF.
- Connect: Low Beam Relay.
- Disconnect: Headlamp Switch C205.
- Ignition ON.
- Measure the voltage between the headlamp switch C205-8, circuit 15-LE29 (GN/BK), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to A6.
No
VERIFY the CJB fuse 158 (10A) is OK. If OK, REPAIR circuit 15-LE29 (GN/BK) 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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A6 BYPASS THE HEADLAMP SWITCH
- Ignition OFF.
- Connect a fused jumper wire between the headlamp switch C205-8, circuit 15-LE29 (GN/BK), harness side and the headlamp switch C205-6, circuit 15S-LE19 (GN/BU), harness side.
- Ignition ON.
- Do the headlamps illuminate?
Yes
REMOVE the jumper wire. INSTALL a new headlamp switch. REFER to Headlamp Switch Service and Repair. TEST the system for normal operation.
No
REPAIR circuit 15S-LE19 (GN/BU) for an open. TEST the system for normal operation.
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