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Pinpoint Test B: DTC C2803




Auxiliary Brake System - Trailer Brake Control (TBC) Module







Pinpoint Tests

Pinpoint Test B: DTC C2803

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. Diagrams By Number

Normal Operation

The brake pressure transducer is attached to the brake master cylinder and is hardwired to the Trailer Brake Control (TBC) module. The transducer can be serviced separated from the master cylinder. The TBC module also receives information from the brake pressure switch (also called the speed control deactivation switch) and the Brake Pedal Position (BPP) switch from the PCM over the High Speed Controller Area Network (HS-CAN) bus. All 3 switches provide the TBC with the current vehicle braking information. The brake pressure switch and the BPP are also used to determine if the transducer is functioning correctly.

The TBC module supplies voltage to the transducer along circuit LCA16 (GN) and ground along circuit RCA16 (BU/BN). The voltage returned from the transducer along circuit VCA13 (YE/BU) is used by the TBC module to determine current brake pressure.

- DTC C2803 (Brake Pressure Transducer Sense Circuit Failure) - If the TBC module detects brake pressure, with no BPP switch input or brake pressure switch input for 200 ms or more, the TBC module will no longer use the pressure transducer input. The TBC module will also set DTC C2803, send TRAILER BRAKE MODULE FAULT to the message center and revert to a limited operating strategy.

This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- BPP switch
- Brake pressure transducer
- Brake pressure switch
- TBC module



PINPOINT TEST B: DTC C2803

NOTICE: Use the Flex Probe Kit for all test connections to prevent damage to the wiring terminals. Do not use standard multi-meter probes.

NOTE: If there is no brake pressure transducer mounted on the brake master cylinder, then the system was not correctly installed. Warranty repairs on incorrectly installed trailer brake systems will not be covered by Ford Motor Company.

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B1 CHECK THE TBC MODULE BRAKE ON/OFF (BOO_TBC) PID


- Connect the scan tool.
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: DataLogger - TBC Module .
- Monitor the BOO_TBC PID while pressing and releasing the brake pedal.
- Does the PID agree with the brake pedal position?

Yes
GO to B3.

No
GO to B2.

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B2 CHECK THE PCM BOO AND BRAKE PRESSURE APPLIED (BPA) PIDs


NOTE: The BOO PID is derived from the BPP (stoplamp) switch and the BPA PID is derived from the speed control deactivation switch.

- Enter the following diagnostic mode on the scan tool: DataLogger - PCM .
- Monitor the BOO and BPA PIDs while pressing and releasing the brake pedal.
- Do the PIDs agree with the position of the brake pedal?

Yes
REFER to Information Bus to diagnose the HS-CAN bus.

No
REFER to Fire Suppression System to diagnose the speed control deactivation switch.

REFER to Lighting and Horns to diagnose the stoplamp (BPP) switch.

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B3 CHECK THE BRAKE PRESSURE TRANSDUCER SIGNAL RETURN CIRCUIT FOR A SHORT TO VOLTAGE


- Ignition OFF.
- Disconnect: TBC Module C2142 .
- Disconnect: Brake Pressure Transducer C147 .
- Ignition ON.
- Measure the voltage between brake pressure transducer C147-2, circuit VCA13 (YE/BU), harness side and ground.




- Is any voltage present?

Yes
REPAIR circuit VCA13 (YE/BU). CLEAR the DTCs. REPEAT the self-test.

No
GO to B4.

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B4 CHECK THE BRAKE PRESSURE TRANSDUCER SIGNAL RETURN CIRCUIT FOR AN OPEN


- Ignition OFF.
- Measure the resistance between TBC module C2142-5, circuit VCA13 (YE/BU), harness side and brake pressure transducer C147-2, circuit VCA13 (YE/BU), harness side.




- Is the resistance less than 5 ohms?

Yes
GO to B5.

No
REPAIR circuit VCA13 (YE/BU). CLEAR the DTCs. REPEAT the self-test.

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B5 ISOLATE THE BRAKE PRESSURE TRANSDUCER


- Connect: TBC Module C2142 .
- Ignition ON.
- Using the scan tool, clear all TBC module DTCs.
- Ignition OFF.
- Ignition ON.
- Firmly press the brake pedal for a minimum of 6 seconds.
- Enter the following diagnostic mode on the scan tool: Self Test - TBC Module .
- Is DTC C2800 set?

Yes
INSTALL a new brake pressure transducer. Make sure to LUBRICATE the O-ring seal with clean, specified brake fluid before installation. REFER to Hydraulic System, Brakes &/or Brake Pedal Assy. CLEAR the DTCs. REPEAT the self-test.

No
GO to B6.

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B6 CHECK FOR CORRECT TBC MODULE OPERATION


- Check the TBC module connector for:
- corrosion.
- pushed-out pins.
- spread terminals.
- Connect the TBC module connector and make sure that it is seated correctly.
- Operate the system and verify the concern is still present.
- Is the concern still present?

Yes
INSTALL a new TBC module. REFER to Trailer Brake Control (TBC) Module Service and Repair. CLEAR the DTCs. REPEAT the self-test.

No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test.

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