Diagnostic Routine AN

Diagnostic Routine AN

Diagnostic Overview

The Trailer Electric Brakes Are Inoperative Or Always Applied

Refer to Wiring Diagram Set 95 for schematic and connector information Electrical Diagrams.

Normal Operation and Fault Conditions

REFER to Trailer Electric Brakes .

Visual Inspection and Diagnostic Pre-checks

- Inspect the BJB (Battery Junction Box) fuses 31 (5A) and 3 (30A).

- Inspect the TBC (Trailer Brake Control) module for damage.

- Inspect the vehicle stoplamps and verify they operate correctly.

- Inspect the trailer tow connector for damage.

- Verify the vehicle stoplamps operate correctly.

Pinpoint Test

NOTE: Before beginning diagnostics, visually inspect the trailer tow connector mounted on the bumper for signs of corrosion or damage. Repair or install a new trailer tow connector as required.

1. CHECK THE TRAILER ELECTRIC BRAKE CONTROLLER FOR A SHORTED OUTPUT

1. Ignition ON.

2. Measure:





Is any voltage present?








2. CHECK THE TBC (Trailer Brake Control) MODULE OUTPUT CIRCUIT FOR A SHORT TO VOLTAGE

1. Disconnect: TBC (Trailer Brake Control) Module.

2. Measure:





Is any voltage present?








3. CHECK THE TBC (Trailer Brake Control) MODULE OUTPUT

1. Ignition OFF.

2. Set the gain on the trailer electric brake controller to the maximum setting.

3. While applying the brake pedal, measure:





Is the voltage greater than 11 volts?








4. CHECK FOR VOLTAGE TO THE TRAILER TOW CONNECTOR (VEHICLE HARNESS)

1. Disconnect: Trailer Tow Connector.

2. NOTE: Make sure the gain is set to the maximum setting.
While applying the brake pedal, measure:





Is the voltage greater than 11 volts?








5. CHECK THE TBC (Trailer Brake Control) MODULE VOLTAGE SUPPLY CIRCUIT FOR AN OPEN

1. Disconnect: TBC (Trailer Brake Control) Module.

2. Measure:





Is the voltage greater than 11 volts?








6. CHECK THE TBC (Trailer Brake Control) MODULE GROUND CIRCUIT FOR AN OPEN

1. Measure:





Is the voltage greater than 11 volts?








7. CHECK THE STOPLAMP SWITCH INPUT TO THE TBC (Trailer Brake Control) MODULE

1. While applying the brake pedal, measure:





Is the voltage greater than 11 volts?








8. CHECK THE STOPLAMP SWITCH INPUT CIRCUIT TO THE TBC (Trailer Brake Control) MODULE FOR AN OPEN

1. Disconnect: BCM (Body Control Module) C2280B.

2. Measure:





Is the resistance less than 3 ohms?








9. CHECK THE TBC (Trailer Brake Control) MODULE OUTPUT CIRCUIT FOR A SHORT TO GROUND

1. Measure:





Is the resistance greater than 10,000 ohms?








10. CHECK THE TBC (Trailer Brake Control) MODULE OUTPUT CIRCUIT FOR AN OPEN

1. Connect a fused jumper wire:





2. Measure:





Is the voltage greater than 11 volts?








11. CHECK FOR CORRECT BCM (Body Control Module) OPERATION

1. Disconnect and inspect all BCM (Body Control Module) connectors.

2. Repair:

- corrosion (install new connector or terminals- clean module pins)
- damaged or bent pins- install new terminals/pins
- pushed-out pins- install new pins as necessary

3. Reconnect the BCM (Body Control Module) connectors. Make sure they seat and latch correctly.

4. Operate the system and determine if the concern is still present.

Is the concern still present?