Pinpoint Test A: The Message Center Displays WIRING FAULT ON TRAILER
Auxiliary Brake System - Trailer Brake Control (TBC) Module
Pinpoint Test A: The Message Center Displays WIRING FAULT ON TRAILER
NOTE: Carry out all pinpoint tests without a trailer connected to the vehicle.
Normal Operation
The braking energy provided to the trailer is varied with a Pulse Width Modulated (PWM) signal that switches between 0 volts and battery voltage, the higher the duty cycle the more braking power available. The Trailer Brake Control (TBC) module varies the PWM (Pulse Width Modulated) signal based on various inputs such as the brake torque message, the manual slider switch and the gain buttons. With the vehicle stationary and 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. When the trailer is connected to the vehicle the Instrument Panel Cluster (IPC) should show the TRAILER CONNECTED message. If the WIRING FAULT ON TRAILER is only message displayed when the trailer is connected, the fault is with the trailer wiring.
Every 4 seconds (when not braking) the TBC (Trailer Brake Control) module sends a voltage pulse to pin 3 of the 7-pin trailer tow connector to determine whether or not a trailer is connected.
- DTC C2806 (Trailer Brakes Wiring Circuit Short to Vbatt)- this DTC sets in continuous memory when the TBC (Trailer Brake Control) module detects that the battery voltage is greater than 9 volts while not braking. The TBC (Trailer Brake Control) module shuts off the trailer brake output and then shuts down.
- DTC C2807 (Trailer Brakes Wiring Circuit Short to Ground)- this DTC sets in continuous memory or on-demand when the TBC (Trailer Brake Control) module detects that the battery voltage drops by more than 20 percent during a braking event or the trailer brakes are drawing more than 28 amps. The TBC (Trailer Brake Control) module shuts off the trailer brake output and then shuts down.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- TBC (Trailer Brake Control) module
- Customer trailer
PINPOINT TEST A : THE MESSAGE CENTER DISPLAYS WIRING FAULT ON TRAILER
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:
Make sure the trailer brakes are electric-magnet actuated drum-type brakes before proceeding with this pinpoint test.
A1 CHECK THE MESSAGE IN THE MESSAGE CENTER
- Verify that a trailer is not connected to the trailer tow connector.
- Ignition ON.
- Allow the TBC (Trailer Brake Control) module time to wake up and prove out.
- Observe the message center.
Does the message center display WIRING FAULT ON TRAILER?
Yes
GO to A2.
No
SEND the trailer to an authorized camper/trailer repair center.
A2 CHECK THE TBC (Trailer Brake Control) MODULE FOR DTCs
- Connect the scan tool.
- Ignition ON.
- Using the scan tool, clear the TBC (Trailer Brake Control) module DTCs.
- Ignition OFF.
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: TBC (Trailer Brake Control) Module Self-Test.
Are any DTCs present?
Yes
For DTC C2806 or C2807, GO to A3.
For all other DTCs, REFER to the Trailer Brake Control (TBC) Module DTC Chart Trailer Brake Control Module.
No
The TBC (Trailer Brake Control) module and vehicle wiring are operating correctly. SEND the trailer to an authorized camper/trailer repair center. CLEAR the DTCs. REPEAT the self-test.
A3 CHECK THE TBC (Trailer Brake Control) MODULE FOR DTCs WITH THE TRAILER TOW CONNECTOR DISCONNECTED
- Using the scan tool, clear the TBC (Trailer Brake Control) module DTCs.
- Disconnect: Trailer Tow Connector C439A.
- Enter the following diagnostic mode on the scan tool: TBC (Trailer Brake Control) Module Self-Test.
Does DTC C2806 or C2807 return?
Yes
For DTC C2806, GO to A5.
For DTC C2807, GO to A4.
No
INSTALL a new trailer tow connector. CLEAR the DTCs. REPEAT the self-test.
A4 CHECK THE TBC (Trailer Brake Control) MODULE PWM (Pulse Width Modulated) OUTPUT CIRCUIT FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: TBC (Trailer Brake Control) module C2142.
- Measure the resistance between the trailer tow connector C439A-3, circuit CAT19 (BU), harness side and ground.
Is the resistance greater than 10,000 ohms?
Yes
GO to A6.
No
REPAIR circuit CAT19 (BU). CLEAR the DTCs. REPEAT the self-test.
A5 CHECK THE TBC (Trailer Brake Control) MODULE PWM (Pulse Width Modulated) OUTPUT CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition ON.
- Measure the voltage between the trailer tow connector C439A-3, circuit CAT19 (BU), harness side and ground.
Is any voltage present?
Yes
REPAIR circuit CAT19 (BU). CLEAR the DTCs. REPEAT the self-test.
No
GO to A6.
A6 CHECK FOR CORRECT TBC (Trailer Brake Control) MODULE OPERATION
- Disconnect the TBC (Trailer Brake Control) module connector.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect the TBC (Trailer Brake Control) module connector and make sure it seats correctly.
- Operate the system and verify the concern is still present.
Is the concern still present?
Yes
INSTALL a new TBC (Trailer Brake Control) module. REFER to Trailer Brake Control (TBC) Module . TEST the system for normal operation.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. TEST the system for normal operation.