Normal Operation

WARNING: This page is about a different car, the 2009 Ford RV Cutaway, 2009 Ford Econoline, 2009 Ford E450 Super Duty, and 2009 Ford Cutaway. However, it is still accessible from the selected car via links, so may be relevant.

When a trailer is connected to the vehicle through the 7-pin trailer connector, the Trailer Brake Control (TBC) module will utilize the trailer as a secondary ground. When the brake pedal is applied, the TBC module will send a Pulse Width Modulated (PWM) voltage to the brake solenoids on the trailer to activate the trailer brakes. Releasing the brake pedal creates a feedback voltage spike that is monitored by the TBC module. Normally, this voltage travels through a diode inside the module and is grounded into the vehicle along circuit GD116 (BK/VT). However, if a condition should occur that prevents the voltage from grounding along circuit GD116 (BK/VT), this feedback voltage will create a voltage potential in the TBC module, this voltage potential is detected by the module and, if the potential is greater than 19 volts, DTC B1863 will be set.

When DTC B1863 is set, the TBC module will disable trailer braking in order to protect the module from additional voltage spikes and the module will also send a TBC FAULT message to the message center.

DTC B1863 (TBC Ground Open Circuit) - An open circuit condition in GD116 (BK/VT) or an internal failure of the TBC module will cause DTC B1863 to set. Unlike the other TBC module DTCs, a trailer must be connected to the 7-pin trailer connector for DTC B1863 to set during an on-demand self test.
This pinpoint test is intended to diagnose the following:
Wiring, terminals or connectors
TBC module