Case IH 4353 – TCU (Tractor Control Unit): EHR FB 1 Shorted to High Source

The sensor feedback voltage on the Electro-Hydraulic Remote (EHR) Feedback 1 circuit was detected as being greater than 4.5 Volts. This indicates a short to a high voltage source (B+ power) in the circuit, a faulty harness, or a failed potentiometer.

• Magnum
• Steiger T4B
• Puma
• Steiger

1. 1

   Visually inspect the Tractor Control Unit (TCU) connector C066 and the implement interface (potentiometer) connector C686.

2. 2

   Ensure the connectors are fully seated, not damaged, the pins are in the correct position, and the fit is tight.

3. 3

   Check for a short to B+ power by using back probes (e.g., SPX/OTC #233788) at the implement interface connector C686 (pin 1). Turn the ignition switch ON and monitor if the voltage exceeds the 4.5V threshold.

1. 1

   Secure the Machine

   Turn off the tractor, lower any implements to the ground, and turn the key to the OFF position.

2. 2

   Inspect and Clean

   Disconnect TCU connector C066 and implement interface connector C686. Clean the contacts with electrical contact cleaner and check for pushed, bent, or corroded pins.

3. 3

   Repair Connectors

   If connector damage is found, repair or replace the connector/pins as required. Reconnect and test if the code clears.

4. 4

   Test the Harness

   If the connectors are good, use a multimeter to test the wiring harness between the TCU and the implement interface for a short to power. If a short is found in the harness, locate the chafe/rub mark and repair the wiring harness.

5. 5

   Replace the Potentiometer

   If the harness and connectors test perfectly fine but the feedback voltage remains out of range (above 4.5V), the implement interface potentiometer has failed internally and must be replaced.

6. 6

   Clear and Verify

   Once the repair is made, use the electronic display or Electronic Service Tool (EST) to clear the fault code. Operate the EHR system to verify the code does not return and the machine returns to proper operation.