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Home >> Ford >> 2009 >> Flex Limited, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 856 (Auxiliary Brake System) >> Diagnostic Tests >> Auxiliary Brake System - Trailer Brake Control (TBC) Module >> Pinpoint Tests >> Pinpoint Test F: The Trailer Brakes Are Inoperative >> Pinpoint Test F: The Trailer Brakes Are Inoperative

Pinpoint Test F: The Trailer Brakes Are Inoperative

WARNING: This page is about a different car, the 2007 Ford Pickup, 2007 Ford F550 Super Duty, 2007 Ford F450 Super Duty, and 2007 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
CAUTION: Use the flex probe kit for all test connections to prevent damage to the wiring terminals. Do not use standard multi-meter probes.
NOTE: Make sure the trailer brakes are electric-magnet actuated drum type brakes before proceeding with this pinpoint test.
  1. F1 CHECK FOR ANY ANTI-LOCK BRAKE SYSTEM (ABS) MODULE DIAGNOSTIC TROUBLE CODES (DTCs) 
    • Key in OFF position.
    • Carry out the ABS module self-test. Retrieve and record any ABS module DTCs.
    • Are any ABS module DTCs retrieved? 
    1. YES  : REFER to VEHICLE DYNAMIC SYSTEMS article.
    2. NO  : Go to  F2.
  2. F2 CHECK THE TRAILER BRAKE CONTROL (TBC) MODULE OUTPUT 
    • Key in ON position.
    • Enter the following diagnostic mode on the diagnostic tool: TBC BOO PID
    • Monitor the TBC BOO PID while firmly pressing and releasing the brake pedal.
    • Does the TBC BOO PID agree with the stoplamp switch? 
    1. YES  : Go to  F3.
    2. NO  : VERIFY brake switch operation. If OK, go to  F4 . If not OK, go to EXTERIOR LIGHTING article.
  3. F3 CHECK CIRCUIT 43 (DB) FOR VOLTAGE 
    NOTE: Battery voltage must be greater than 10 volts.
    • Key in OFF position.
    • Disconnect: Trailer Tow C4099
    • Key in ON position.
    • Have an assistant press the manual slider switch fully to the left with a gain of 10 on the TBC module.
    • Measure the voltage between trailer tow C4099-3, circuit 43 (DB), harness side and ground.
    • Is the voltage greater than 10-12 volts? 
    1. YES  : The TBC module is operating correctly. SEND the trailer to an authorized camper/trailer repair center for an overload condition.
    2. NO  : Go to  F4.
  4. F4 CHECK CIRCUIT 43 (DB) FOR AN OPEN 
    • Key in OFF position.
    • Disconnect: TBC Module C2142a
    • Measure the resistance between trailer tow C4099-3, circuit 43 (DB), harness side and TBC C2142a-3, circuit 43 (DB), harness side.
      • Fig 1: Checking Circuit 43 (DB) For Open
      GF0006754Courtesy of FORD MOTOR CO.
    • Is the resistance less than 5 ohms? 
    1. YES  : The system is operating correctly at this time. The concern may have been caused by the customer's trailer or a loose or corroded connector. TEST the system for normal operation.
    2. NO  : REPAIR circuit 43 (DB) for an open. TEST the system for normal operation.
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