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Home >> Ford >> 2012 >> Mustang Base, 2D Coupe, Automatic Trans >> Repair and Diagnosis >> External Pages >> Different car >> Section 74 (Auxiliary Brake System -- F250-F550 Super Duty) >> Diagnosis And Testing >> Auxiliary Brake System - Trailer Brake Control (TBC) Module >> Pinpoint Tests >> Pinpoint Test B: The Trailer Brakes are Always Engaged >> Normal Operation

Normal Operation

WARNING: This page is about a different car, the 2012 Ford Pickup, 2012 Ford F550 Super Duty, 2012 Ford F450 Super Duty, and 2012 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.

The braking energy provided to the trailer is varied with a Pulse Width Modulated (PWM) signal that switches between 0 volts 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 more than 10-12 volts supplied to pin 3 of the 7-pin trailer tow connector. The TBC module also receives information from the brake pressure switch (also called the speed control deactivation switch) and the 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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