Pinpoint Test R: The Fog Lamps Are Inoperative
Fog Lamps
Pinpoint Test R: The Fog Lamps Are Inoperative
Refer to Wiring Diagram Set 86, Fog Lamps for schematic and connector information Electrical Diagrams.
Normal Operation
The Smart Junction Box (SJB) sends a reference signal to the headlamp switch to monitor the fog lamp request. When the fog lamp switch is engaged, the voltage signal is routed to ground.
When the SJB (Smart Junction Box) detects the fog lamps on request, the SJB (Smart Junction Box) provides ground to the fog lamp relay coil (integrated into the SJB (Smart Junction Box)). When the fog lamp relay is energized, voltage is routed to the fog lamps.
For Navigator, both fog lamps share the same ground.
This pinpoint test is intended to diagnose the following:
- Fuse
- Wiring, terminals or connectors
- Headlamp switch
- SJB (Smart Junction Box)
PINPOINT TEST R : THE 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.
R1 CHECK THE HEADLAMP SWITCH PID
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: SJB (Smart Junction Box) DataLogger.
- Monitor the SJB (Smart Junction Box) (FOG SW) PID while engaging the fog lamp switch.
Does the PID indicate the fog lamp switch is active?
Yes
For Navigator, GO to R5.
For Expedition, GO to R6.
No
GO to R2.
R2 CHECK FOR VOLTAGE TO THE HEADLAMP SWITCH
- Ignition OFF.
- Disconnect: Headlamp Switch C205.
- Measure the voltage between the headlamp switch C205-6, circuit CLF29 (BN), harness side and ground.
Is the voltage greater than 10 volts?
Yes
GO to R3.
No
GO to R4.
R3 CHECK FOR VOLTAGE TO THE HEADLAMP SWITCH USING THE CONNECTOR GROUND
- Measure the voltage between the headlamp switch C205-6, circuit CLF29 (BN), harness side and the headlamp switch C205-7, circuit GD138 (BK/WH), harness side.
Is the voltage greater than 10 volts?
Yes
INSTALL a new headlamp switch. REFER to Headlamp Switch . TEST the system for normal operation.
No
REPAIR circuit GD138 (BK/WH) for an open. TEST the system for normal operation.
R4 CHECK THE FOG LAMP REQUEST CIRCUIT FOR AN OPEN
- Disconnect: SJB (Smart Junction Box) C2280B.
- Measure the resistance between the headlamp switch C205-6, circuit CLF29 (BN), harness side and the SJB (Smart Junction Box) C2280B-49, circuit CLF29 (BN), harness side.
Is the resistance less than 5 ohms?
Yes
GO to R7.
No
REPAIR circuit CLF29 (BN) for an open. TEST the system for normal operation.
R5 CHECK FOR VOLTAGE TO THE LH FOG LAMP
- Ignition OFF.
- Disconnect: LH Fog Lamp C1322.
- Ignition ON.
- Place the headlamp switch in the PARKING LAMPS ON position and engage the fog lamp switch.
- Measure the voltage between the LH fog lamp C1322-B, circuit CLF21 (GY/VT), harness side and ground.
Is the voltage greater than 10 volts?
Yes
REPAIR circuit GD120 (BK/GN) for an open. TEST the system for normal operation.
No
GO to R6.
R6 CHECK THE SJB (Smart Junction Box) FOG LAMP OUTPUT CIRCUIT FOR AN OPEN
- Ignition OFF.
- Connect: LH Fog Lamp C1322 (Navigator).
- Disconnect: SJB (Smart Junction Box) C2280E.
- Connect a fused jumper wire between the SJB (Smart Junction Box) C2280E-1, circuit CBB56 (BU/GN), harness side and the SJB (Smart Junction Box) C2280E-3, circuit CLF21 (GY/VT), harness side.
- Ignition ON.
Do the fog lamps illuminate?
Yes
REMOVE the jumper wire. GO to R7.
No
REMOVE the jumper wire. VERIFY the SJB (Smart Junction Box) fuse 21 (15A) is OK. If OK, REPAIR circuit CLF21 (GY/VT) 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 Electrical Diagrams.
R7 CHECK FOR CORRECT SJB (Smart Junction Box) OPERATION
- Disconnect all the SJB (Smart Junction Box) connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the SJB (Smart Junction Box) 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 (Smart Junction Box). 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.