Case IH 519072-04 - UCM – UCM: Rear hitch left draft sensor - voltage low

The control module is receiving a signal voltage from the left rear hitch draft sensor (load pin) that is below the minimum acceptable threshold. This condition is typically caused by a short to ground in the signal wire, a loss of the sensor's reference voltage (open circuit), or an internal failure of the sensor itself.

• MAGNUM AFS Connect
• Steiger AFS Connect
• Puma AFS Connect

1. 1

   Inspect the left draft sensor (located at the pivot point of the left lower link arm on the rear hitch) and its electrical connector for physical damage, mud/moisture ingress, or corroded pins.

2. 2

   Check the wiring harness between the left draft sensor and the UCM for chafing, pinched wires, or a short to ground.

3. 3

   With the key ON, disconnect the sensor and verify that the 5V/8V reference voltage and ground are present at the connector.

4. 4

   Swap the left and right draft sensors. If the fault code changes to the right side (e.g., 519073-04), the sensor is internally shorted and defective. If the fault remains on the left side, the issue is in the tractor's wiring harness or the UCM itself.

1. 1

   Relieve tension

   Lower the rear hitch completely to the ground and disconnect any attached implements to remove all load and tension from the lower link arms.

2. 2

   Power down

   Turn off the tractor and disconnect the battery to prevent electrical spikes.

3. 3

   Disconnect wiring

   Unplug the electrical harness from the left draft sensor pin.

4. 4

   Remove hardware

   Remove the retaining bolt and locking plate/bracket that secures the draft pin to the tractor chassis.

5. 5

   Extract the pin

   Carefully drive or slide the faulty draft pin out of the lower link arm and chassis bore.

6. 6

   Install new sensor

   Clean the bore. Slide the new draft sensor pin into place. Crucial Step: Ensure the alignment flat/notch on the pin is oriented exactly as specified in the service manual (usually facing a specific direction to measure horizontal draft force accurately).

7. 7

   Reassembly

   Secure the pin with the retaining plate and bolt, then reconnect the electrical harness.

8. 8

   Calibration

   Power on the tractor. You must perform a Rear Hitch / Electronic Draft Control (EDC) calibration via the AFS Pro display or a dealer diagnostic tool. This allows the UCM to learn the new sensor's baseline zero-load voltage.