F 350 2WD Super Duty V10-6.8L (2009)
Pinpoint Test H: The Trailer Brakes Are Always Engaged And/Or The Message Center
Intermittently Displays Trailer Disconnected O
Auxiliary Brake System - Trailer Brake Control (TBC) Module
Pinpoint Tests
Pinpoint Test H: The Trailer Brakes are Always Engaged and/or The Message Center Intermittently Displays TRAILER DISCONNECTED or
WIRING FAULT ON TRAILER While Towing a Trailer
NOTE: Carry out all pinpoint tests without a trailer connected to the vehicle.
Refer to Wiring Diagram Set 95, Trailer/Camper Adapter for schematic and connector information. See: Diagrams/Electrical Diagrams/Diagrams By
Number
Normal Operation
The braking energy that is provided to the trailer is varied with a Pulse Width Modulated (PWM) signal that switches between 0 volt and battery voltage,
according to the Trailer Brake Control (TBC) module gain setting, the higher the duty cycle the more braking power available. With the vehicle
stationary and with the manual slider switch fully to the left with a gain of 10, there should be greater than 10-12 volts supplied to trailer tow C4099-3
circuit CAT19 (BU). The TBC module also receives information from the brake pressure switch (also called the speed control deactivation switch) and
the Brake Pedal Position (BPP) (stoplamp) switch from the PCM over the High Speed Controller Area Network (HS-CAN) bus.
This pinpoint test is intended to diagnose the following:
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Fuse(s)
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Wiring, terminals or connectors
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TBC module
PINPOINT TEST H: THE TRAILER BRAKES ARE ALWAYS ENGAGED AND/OR THE MESSAGE CENTER INTERMITTENTLY
DISPLAYS TRAILER DISCONNECTED OR WIRING FAULT ON TRAILER WHILE TOWING A TRAILER
NOTICE: Use the Flex Probe Kit for all test connections to prevent damage to the wiring terminals. Do not use standard multi-meter probes.
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H1 CHECK FOR TBC MODULE DTCs
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Review the DTCs retrieved and recorded during Inspection and Verification.
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Are any TBC module DTCs present?
Yes
GO to the Trailer Brake Control (TBC) Module DTC Chart. See: Diagnostic Trouble Code Descriptions
No
GO to H2.
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H2 CHECK THE TBC BRAKE ON/OFF (BOO_TBC) PID
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Connect the scan tool.
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Ignition OFF.
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Enter the following diagnostic mode on the scan tool: DataLogger - TBC Module.
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Monitor the BOO_TBC PID while pressing and releasing the brake pedal.
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Does the PID agree with the brake pedal position?
Yes
GO to H4.
No
GO to H3.
