Case IH 56120 – Transmission Controller (TRANS / TCU): Trans Controller Failure -- Internal short in the System Pressure Valve Coil circuit.

The transmission controller has commanded the system pressure valve coil driver to the "OFF" state, but the controller still senses current flowing through the driver. This indicates an internal hardware failure within the controller itself (specifically, the system pressure valve coil driver has failed).

• STX Steiger
• Case IH Steiger STX Series
• STX275
• STX325
• STX375
• STX425
• STX440
• STX450
• STX500
• TJ275
• TJ325
• TJ375
• TJ425
• TJ450
• TJ500

1. 1

   Inspect the wiring harness running from the transmission controller to the system pressure valve solenoid for chafing and shorts to a power source.

2. 2

   Check the system pressure valve solenoid coil for an internal short, especially if the problem is temperature-sensitive.

3. 3

   Verify normal operation voltage, noting that the system pressure solenoid is powered at all times unless the transmission controller actively removes power.

1. 1

   Power Down

   Turn off the tractor and disconnect the battery to prevent electrical arcing or further module damage.

2. 2

   Locate and Remove the TCU

   Locate the Transmission Controller. Carefully disconnect the multi-pin wiring harnesses from the module.

3. 3

   Dismount

   Remove the mounting hardware securing the failed transmission controller and remove it from the machine.

4. 4

   Install the New TCU

   Mount the replacement Transmission Control Module and secure the hardware.

5. 5

   Reconnect

   Reconnect the wiring harnesses, ensuring the connectors are fully seated and locked. Reconnect the battery.

6. 6

   Calibrate and Clear Codes

   Turn the key on. You will need to enter the "TRANS SETUP" menu on the cab display to calibrate the new transmission controller. Once calibration is complete, retrieve and clear the inactive 56120 fault code from the system memory.