Case IH 2418 – Transmission Control Unit: Low / high range synchronizer potentiometer - voltage too low

The transmission control system is receiving a voltage signal from the low/high range synchronizer potentiometer that falls below the minimum calibrated threshold. This typically points to a wiring issue, a disconnected harness, or a failure of the potentiometer itself.

• Optum
• Magnum MX210
• Magnum MX230
• Magnum MX255
• Magnum MX285
• Puma

1. 1

   Verify that the tractor battery has not been connected to an external power supply (like a jump starter). If it is, disconnect it and test the system for normal operation.

2. 2

   Inspect the low/high range synchronizer potentiometer connector (X-666) and the CCU connector (X-097). Ensure they are securely connected, undamaged, pins are in the correct position, and the fit is tight.

3. 3

   Disconnect connector X-666. Turn the ignition switch ON. Measure the voltage between connector X-666 pin 3 (wire 7525G - Green) and a good ground. If it does not read approximately 5 Volts, the wire harness needs repair or replacement.

4. 4

   Measure between connector X-666 pin 1 (wire 60BT - Black/White) and ground. If an open circuit is indicated, repair the harness.

5. 5

   Turn the ignition OFF. Disconnect connector X-956. Measure continuity between connector X-666 pin 2 (wire 7960 - Violet) and connector X-956 pin 18 (wire 7960 - White). If an open circuit is found, repair the harness.

6. 6

   Turn the ignition ON. Measure the voltage between connector X-666 pin 2 (wire 7960 - Violet) and ground. If any voltage is indicated, there is a short to power in the harness that must be repaired.

1. 1

   Replace the Sensor

   Remove and replace the low/high range synchronizer potentiometer.

2. 2

   Recalibrate/Test

   Clear the fault codes and test the transmission by shifting through the ranges to ensure the synchronizer engages properly and the code does not return.

3. 3

   Software Update

   If the fault is still present after replacing the potentiometer, download/flash the correct level of software to the transmission controller.

4. 4

   Module Replacement

   If the fault recurs even after a software update and sensor replacement, the UCM (Unit Control Module) is likely internally faulted and must be removed and replaced.