Case IH 2420 – CCU (Central Control Unit): Low / high range synchronizer potentiometer - voltage is out of calibrated range

The voltage signal returning from the low/high range synchronizer potentiometer is falling outside of its expected, calibrated parameters. The potentiometer monitors the physical position of the synchronizer. When the voltage is out of range, the control module cannot accurately determine the synchronizer's position, which can prevent the transmission from shifting properly between low and high ranges.

• Optum
• Puma Series (Puma 140, 165, 180, 195, 210, 225)
• Maxxum Series
• Steiger Series

1. 1

   Attempt to perform the transmission calibration procedure.

2. 2

   Check that the tractor battery has not been connected to an external power supply (like a jump box or improper charger), which can cause voltage anomalies. Disconnect any external supply and retest.

3. 3

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

4. 4

   Disconnect connector X-666 and turn the ignition switch to the ON position. Measure the connector to ensure the CCU is supplying a 5-Volt reference signal to the potentiometer.

5. 5

   Disconnect the low range solenoid connector (X-641) and the high range solenoid connector (X-643). Measure the resistance between terminal 1 and terminal 2 on each solenoid.

1. 1

   Recalibrate

   Run the electronic transmission calibration. If the code persists, proceed to step 2.

2. 2

   Repair Wiring

   If the visual inspection of connectors X-666 and X-097 reveals damaged pins, corrosion, or loose wires, repair or replace the affected wiring harness section. If the 5V reference is missing, trace the harness back to the CCU to repair the open/short circuit.

3. 3

   Replace Solenoids

   Evaluate the resistance readings from the low and high range solenoids. If the resistance indicated is not between 7 to 11 Ohms (some OEM manual revisions specify 8 to 11 Ohms), remove and replace the faulty clutch solenoid.

4. 4

   Replace Potentiometer

   If the wiring is intact, the 5V reference is present, and the solenoids test within specification, the low/high range synchronizer potentiometer itself has likely failed internally. Replace the potentiometer and recalibrate the transmission.

5. 5

   Hydraulic/Mechanical Testing

   If the error code remains after replacing the electrical components, the transmission may have an internal mechanical or hydraulic fault (e.g., a jammed synchronizer). Perform a transmission hydraulic pressure test as outlined in the OEM service manual to diagnose internal driveline issues.