Case IH 1028 - UCM – UCM: Lift arm position sensor – voltage too high

This code indicates that the signal voltage returning from the rear 3-point hitch lift arm position sensor (potentiometer) has exceeded the maximum expected threshold. This typically points to a short to power (+12V) in the sensor signal wire, an internal failure of the potentiometer, or a broken/disconnected mechanical linkage causing the sensor to over-rotate.

• VESTRUM CVX
• Puma Series
• Magnum Series
• Steiger Series
• CX Series
• MX Series

1. 1

   Inspect the mechanical sensor lever and connecting rod attached to the rockshaft/lift arm. If the linkage is bent, broken, or disconnected, the sensor may rotate past its normal operating range.

2. 2

   Inspect the chassis harness leading to the lift arm position sensor. Look for rubbed wires that could be shorting the signal wire to a +12V power source.

3. 3

   Disconnect the sensor and check the connector with a multimeter. Ensure the 5-volt reference circuit is supplying exactly 5V and that the ground circuit has good continuity.

4. 4

   If the wiring is intact, test the sensor's resistance with a multimeter while manually moving the linkage. If the resistance drops to zero or shows an open circuit at certain points, the potentiometer is internally shorted/failed.

1. 1

   Power Down

   Turn the ignition key to the OFF position and disconnect the battery ground cable to protect the UCM.

2. 2

   Disconnect Linkage

   Locate the lift arm position sensor at the rear of the tractor near the rockshaft. Unbolt the sensor connecting rod/lever from the sensor drive element.

3. 3

   Remove Sensor

   Unplug the electrical connector from the sensor. Remove the mounting bolts securing the sensor to the tractor chassis and remove the unit.

4. 4

   Install New Sensor

   Mount the replacement lift arm potentiometer and secure the bolts.

5. 5

   Reconnect

   Reattach the mechanical sensor lever/rod and plug in the electrical connector.

6. 6

   Hitch Calibration

   Reconnect the battery. Turn the key ON; the ADIC (instrument cluster) will build a list of CAN controllers. Enter the 'H' Menu (Calibration Menu) to run the automatic detection and calibration procedure for the EDC/lift arms so the UCM can learn the new minimum and maximum voltage limits.