Expedition 2WD V8-5.4L (2009)
The trailer battery charge relay coil receives voltage from the Smart Junction Box (SJB) fuse 42 (10A) through circuit CAT23 (GY/YE) when the
ignition switch is in the RUN position. Ground for the trailer battery charge relay coil is supplied through circuit GD123 (BK/GY). The Battery Junction
Box (BJB) fuse 21 (30A) supplies voltage to the trailer battery charge relay switch side through circuit SBB21 (GY/RD). When the trailer battery charge
relay is energized, the voltage is routed to the trailer tow connector through circuit CAT14 (OG).
This pinpoint test is intended to diagnose the following:
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Fuse
-
Wiring, terminals or connectors
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Trailer battery charge relay
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Trailer
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SJB
PINPOINT TEST AD: THE TRAILER BATTERY CHARGING IS INOPERATIVE/DOES NOT OPERATE CORRECTLY
NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the
connector.
NOTE: Before beginning diagnostics, visually inspect the trailer tow connector for signs of corrosion or damage. Repair or install a new trailer tow
connector as required.
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AD1 CHECK FOR VOLTAGE THROUGH THE TRAILER TOW CONNECTOR (BATTERY CHARGE INOPERATIVE)
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Ignition ON.
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Measure the voltage between the trailer tow connector pin 5, circuit CAT14 (OG), component side and ground.
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Is the voltage greater than 10 volts?
Yes
GO to AD8.
No
GO to AD2.
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AD2 CHECK FOR VOLTAGE AT THE TRAILER TOW CONNECTOR (BATTERY CHARGE INOPERATIVE)
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Ignition OFF.
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Disconnect: Trailer Tow C4099.
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Ignition ON.
-
Measure the voltage between the trailer tow C4099-5, circuit CAT14 (OG) and ground.
-
Is the voltage greater than 10 volts?
Yes
INSTALL a new trailer tow connector. TEST the system for normal operation.
