Case IH 6003 – TCU: Brake light relay fault

The system has detected an electrical anomaly in the relay circuit, specifically logging one of two conditions: a short circuit to 12 volts, or an open circuit or a short to ground.

• Magnum
• Steiger T4B
• Case IH Magnum 235 – 340 (Series 4)
• Case IH STX Steiger Series (350 to 600 HP)
• Case IH Steiger 485
• Case IH MX Magnum Series

1. 1

   Clear the error code with an approved diagnostic tool, run the tractor under normal conditions, and retest to see if the code returns

2. 2

   Check the fuse panel for a blown fuse related to the brake light or MFD system

3. 3

   Test the brake switch relay for internal failure

4. 4

   Disconnect the TCU connector and the relay/solenoid connector, then measure resistance between the pins to ensure there is no open circuit in the wiring harness

5. 5

   Test the harness pins against a ground source to check for a short to ground, and test between harness pins to check for a short circuit to 12V

1. 1

   Replace Blown Fuses

   If the diagnostic checks reveal a blown fuse, replace it. If it blows again immediately, proceed to wiring checks.

2. 2

   Replace Faulty Relay

   If the brake light relay fails a bench test (e.g., open coil or stuck contacts), remove and replace the relay.

3. 3

   Repair Wiring Harness

   If an open circuit, short to ground, or short to 12V is found during multimeter testing, trace the wiring harness between the brake light relay and the TCU. Repair the damaged wires or replace the harness section as required.

4. 4

   Update TCU Software

   If the harness, fuses, and relay are all in good working order but the fault re-occurs, connect the diagnostic tool and download the correct, most up-to-date level of software to the TCU.

5. 5

   Replace the TCU

   If the software update does not resolve the issue and all physical circuits are verified good, the Tractor Control Unit (TCU) has suffered an internal failure and must be removed and replaced.