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.

The braking energy that is provided to the trailer is varied with a Pulse Width Modulated (PWM) signal along circuit CAT19 (BU) that switches between 0 volt and battery voltage, the higher the duty cycle the more braking power available. The Trailer Brake Control (TBC) module varies the PWM signal based on various inputs such as the pressure transducer(s), the manual slider switch and the gain buttons. 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 receives Brake Pedal Position (BPP) (stoplamp) switch information from the PCM over the High Speed Controller Area Network (HS-CAN) bus. The TBC module also receives several sensor input messages (brake pressure switch, wheel speed, sensor cluster, ABS system status, etc.) from the ABS module over the HS-CAN bus. If there is a problem in the ABS module that is preventing this information from being sent to the TBC module, the TBC module will enter a limited operating mode. The TBC module receives fused battery voltage from Battery Junction Box (BJB) fuse 18 (30A) along circuit SBB18 (YE/RD) and fused ignition voltage from Smart Junction Box (SJB) fuse 33 (10A) along circuit CBP33 (WH/BN). The ground path for the TBC module is along circuit GD116 (BK/VT).

This pinpoint test is intended to diagnose the following:

Fuse(s)
Wiring, terminals or connectors
ABS module
TBC module
Customer trailer