Pinpoint Test A: DTC B1863
Auxiliary Brake System - Trailer Brake Control (TBC) Module
Pinpoint Tests
Pinpoint Test A: DTC B1863
Refer to Wiring Diagram Set 95, Trailer/Camper Adapter for schematic and connector information. Diagrams By Number
Normal Operation
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 Pulse Width Modulated (PWM) voltage that the TBC module sends to the trailer actuates solenoids that actuate the trailer brakes. When the solenoids open, a voltage spike occurs that is fed back to the TBC module. Normally, this voltage travels through a diode inside the module and is grounded into the vehicle along circuit GD138 (BK/WH). However, if a condition should occur that prevents the voltage from grounding along circuit GD138 (BK/WH), this feed-back voltage will travel through the TBC module but will then travel back through the trailer and then be grounded through the 7-pin trailer connector into the vehicle. When the feed-back voltage is grounded in this manner, it 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 GD138 (BK/WH) 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
PINPOINT TEST A: DTC B1863
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: A trailer must be connected to the 7-pin trailer connector for DTC B1863 to set during the on-demand self test.
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A1 CHECK THE TBC MODULE GROUND CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect: TBC Module C2142.
- Measure the resistance between TBC module C2142-3, circuit GD138 (BK/WH), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
GO to A2.
No
REPAIR circuit GD138 (BK/WH). CLEAR the DTCs. REPEAT the self-test.
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A2 CHECK FOR CORRECT TBC MODULE OPERATION
- Check the TBC module connector for:
- corrosion.
- pushed-out pins.
- spread terminals.
- Connect: TBC Module C2142.
- Make sure the connector is seated correctly, then operate the system and verify the concern is still present.
- Is the concern still present?
Yes
INSTALL a new TBC module. 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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