Pinpoint Test Q: Both Fog Lamps Are Inoperative
Fog Lamps
Pinpoint Tests
Pinpoint Test Q: Both Fog Lamps Are Inoperative
Refer to Wiring Diagram Set 86, Fog Lamps for schematic and connector information. Diagrams By Number
Normal Operation
The Smart Junction Box (SJB) sends a voltage reference signal to the headlamp switch through circuit CLF21 (GY/VT) to monitor the fog lamp request. When the fog lamp switch is engaged, the voltage signal is routed to ground.
When the SJB detects the fog lamps on request, the SJB provides ground to the fog lamp relay coil (integral to the SJB). When the fog lamp relay is energized, voltage is routed through circuit CLF12 (BN/YE) to the fog lamps.
This pinpoint test is intended to diagnose the following:
- Fuse
- Wiring, terminals or connectors
- Headlamp switch
- SJB
PINPOINT TEST Q: BOTH FOG LAMPS 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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Q1 CHECK THE HEADLAMP SWITCH PID
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: SJB DataLogger.
- Monitor the SJB headlamp switch PID (FOG SW) while engaging the fog lamp switch.
- Does the PID indicate the fog lamp switch is on?
Yes
GO to Q4.
No
GO to Q2.
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Q2 CHECK THE HEADLAMP SWITCH
- Ignition OFF.
- Disconnect: Headlamp Switch C205.
- Carry out the headlamp switch component test.
- Is the headlamp switch OK?
Yes
GO to Q3.
No
INSTALL a new headlamp switch. REFER to Headlamp Switch Service and Repair. TEST the system for normal operation.
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Q3 CHECK CIRCUIT CLF21 (GY/VT) FOR AN OPEN
- Disconnect: SJB C2280b.
- Measure the resistance between the headlamp switch C205-6, circuit CLF21 (GY/VT), harness side and the SJB C2280b-49, circuit CLF21 (GY/VT), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to Q5.
No
REPAIR the circuit. TEST the system for normal operation.
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Q4 CHECK CIRCUIT CLF12 (BN/YE) FOR AN OPEN
- Ignition OFF.
- Disconnect: SJB C2280e.
- Connect a fused jumper wire between the SJB C2280e-1, circuit CDC32 (BN/YE), harness side and the SJB C2280e-3, circuit CLF12 (BN/YE), harness side.
- Ignition ON.
- Do the fog lamps illuminate?
Yes
REMOVE the jumper wire. VERIFY the SJB fuse 21 (15A) is OK. If OK, GO to Q5. If not OK, REFER to Wiring Diagrams to identify the possible causes of the circuit short.
No
REMOVE the jumper wire. REPAIR the circuit. TEST the system for normal operation.
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Q5 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. 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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