Case IH 12561 – MTA CCM & APH: NO Trailer brake – relay system

This indicates an electrical fault (such as an open circuit, short circuit, or component failure) within the trailer brake relay control circuit, preventing the system from properly actuating the trailer brakes when commanded.

• MAXXUM T4E
• VESTRUM CVX
• Farmall
• Maxxum
• Puma
• Magnum

1. 1

   Locate the trailer brake relay in the cab fuse/relay panel (often designated in the manual as a specific chassis or cab relay, such as 263F depending on the model).

2. 2

   Check the associated fuses for the trailer brake and PTO circuits (often a 5A or 20A fuse in the cab distribution box) to ensure they are not blown.

3. 3

   Remove the trailer brake relay and test the coil resistance and contact continuity using a multimeter.

4. 4

   Check the relay socket for burnt pins, pushed-out terminals, or corrosion. Inspect the wiring harness running from the CCM/APH to the relay block for chafing or breaks.

5. 5

   Verify that the trailer brake pressure switch and the parking brake switch are functioning correctly, as these inputs dictate the relay's operation.

1. 1

   Power Down

   Turn off the tractor, remove the key, and engage the parking brake.

2. 2

   Access the Panel

   Open the cab fuse and relay access panel.

3. 3

   Remove the Relay

   Pull the faulty trailer brake relay from its socket.

4. 4

   Clean the Socket

   If there is any dirt or light corrosion, spray the socket with electrical contact cleaner and let it dry.

5. 5

   Install the New Part

   Insert the replacement OEM relay firmly into the socket.

6. 6

   Clear the Code

   Connect a compatible diagnostic tool (such as the Case IH EST or Jaltest diagnostic tool) to the tractor's diagnostic port, read the active codes, and clear fault code 12561.

7. 7

   System Test

   Start the tractor and actuate the service brakes and parking brake to ensure the trailer brake relay clicks over and the system pressurizes correctly without triggering the code.