Case IH 2426-03 - UCM – UCM: Auto depth control position feedback sensor - Voltage Above Normal, or Shorted to High Source

The controller is receiving a signal voltage from the depth control potentiometer that is higher than the maximum allowable threshold (typically near or above the 5V reference). This is almost always caused by an open ground circuit, a signal wire shorted to a power source, or an internal failure (open circuit) within the sensor itself.

• MAGNUM AFS Connect
• Steiger & Quadtrac Series (450, 470, 500, 540, 580, 620)
• Magnum Series (250, 260, 280, 310, 340, 380)
• Puma Series (150, 165, 175, 180-260 CVX)

1. 1

   Visual Inspection: Inspect the wiring harness and connector at the depth control position feedback sensor (located on the rear lift linkage or implement draft linkage) for torn wires, corrosion, or moisture.

2. 2

   Sensor Disconnect Test: Unplug the sensor and turn the key ON. Check if the active fault code changes from 2426-03 (Voltage High) to a Voltage Low code (e.g., FMI 04). If it changes, the wiring harness is intact and the sensor has failed internally.

3. 3

   Voltage & Ground Verification: With the sensor unplugged, use a multimeter to measure the pins on the harness side. Verify a steady 5V reference on the supply pin and good continuity to the chassis/UCM ground on the ground pin (an open ground wire causes the signal voltage to float high).

4. 4

   Short to Power Check: Test the signal wire for continuity to the 5V or 12V power circuits. If voltage is present on the signal wire while disconnected from the sensor, the harness is shorted.

1. 1

   Power Down

   Turn off the tractor and engage the battery disconnect switch to protect the UCM.

2. 2

   Remove the Sensor

   Disconnect the electrical harness from the faulty auto depth control potentiometer. Unbolt the sensor from the lift/draft linkage assembly. Note the physical orientation of the sensor arm or rotary shaft before removal.

3. 3

   Install the New Sensor

   Mount the replacement position feedback sensor. Ensure the mechanical linkage is properly aligned so the sensor does not over-travel or bind during the full physical stroke of the hitch/implement.

4. 4

   Reconnect

   Plug the electrical harness back into the sensor.

5. 5

   Clear Codes

   Turn the battery disconnect back on, power up the tractor, and verify that the 2426-03 fault code is now inactive.

6. 6

   System Calibration

   Because a new potentiometer will have slightly different voltage outputs at physical resting points, you must calibrate the auto depth control system. Access the tractor's display (e.g., Pro 700, AFS Connect) or use the Case IH Electronic Service Tool (EST) to perform a hitch/depth control calibration.