F 550 4WD Super Duty V10-6.8L (2009)
The Smart Junction Box (SJB) monitors the instrument panel dimmer switch status on circuit CLN28 (GN/BU) to determine if the courtesy lamps are
requested. Based on the instrument panel dimmer switch status, the SJB supplies voltage to the courtesy lamps through circuit CLN03 (YE/GY).
This pinpoint test is intended to diagnose the following:
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Wiring, terminals or connectors
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Dimmer switch
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SJB
PINPOINT TEST I: THE COURTESY LAMPS ARE INOPERATIVE FROM THE INSTRUMENT PANEL DIMMER SWITCH
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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I1 CHECK THE INSTRUMENT PANEL DIMMER SWITCH
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Ignition OFF.
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Disconnect: Instrument Panel Dimmer Switch C2065.
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Connect a fused jumper wire between the instrument panel dimmer switch C2065-2, circuit CLN28 (GN/BU), harness side and the instrument
panel dimmer switch C2065-4, circuit RLN29 (WH/OG), harness side.
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Do the courtesy lamps illuminate?
Yes
REMOVE the jumper wire. INSTALL a new instrument panel dimmer switch. TEST the system for normal operation.
No
REMOVE the jumper wire. GO to I2.
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I2 CHECK CIRCUIT CLN28 (GN/BU) FOR A SHORT TO VOLTAGE
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Disconnect: SJB C2280b.
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Ignition ON.
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Measure the voltage between the SJB C2280b-51, circuit CLN28 (GN/BU), harness side and ground.
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Is any voltage present?
Yes
REPAIR the circuit. TEST the system for normal operation.
No
GO to I3.
