Expedition 2WD V8-5.4L (2009)
Parking, Rear and License Plate Lamps
Pinpoint Tests
Pinpoint Test Q: The Parking, Rear Or License Plate Lamps Are On Continuously
Refer to Wiring Diagram Set 92, Parking, Rear and License Lamps for schematic and connector information. See: Diagrams/Electrical
Diagrams/Diagrams By Number
Normal Operation
The Smart Junction Box (SJB) monitors the parking lamp request input from the headlamp switch through circuit CLS05 (BU/GY). The SJB provides a
ground for the parking lamp relay coil (integrated into the SJB) when a request for the parking lamps is received. When the parking lamp relay is
energized, voltage is routed through circuit CLS30 (VT/WH) to the rear and front parking lamps.
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DTC B1578 (Lamp Park Input Circuit Short to Ground) - an on-demand DTC that may set when the SJB detects a short to ground in the parking
lamps on input circuit.
This pinpoint test is intended to diagnose the following:
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Wiring, terminals or connectors
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Headlamp switch
-
SJB
PINPOINT TEST Q: THE PARKING, REAR OR LICENSE PLATE LAMPS ARE ON CONTINUOUSLY
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Q1 USE THE RECORDED DTCs FROM THE SJB SELF-TEST
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Check the recorded results from the SJB self-test.
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Was DTC B1578 recorded?
Yes
GO to Q2.
No
GO to Q4.
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Q2 CHECK THE HEADLAMP SWITCH
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Ignition OFF.
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Disconnect: Headlamp Switch C205.
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Carry out the headlamp switch component test.
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Is the headlamp switch OK?
Yes
GO to Q3.
No
INSTALL a new headlamp switch. REFER to Headlamp Switch See: Headlamp/Headlamp Switch/Service and Repair. CLEAR the DTCs. REPEAT the
self-test.
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Q3 CHECK CIRCUIT CLS05 (BU/GY) FOR A SHORT TO GROUND
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Disconnect: SJB C2280b.
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Measure the resistance between the headlamp switch C205-5, circuit CLS05 (BU/GY), harness side and ground.