Case IH 517743-04 - UCM – UCM: Rear hitch position sensor voltage low

The rear hitch position sensor's signal voltage has dropped below the normal operating range. This underlying condition is typically caused by an open circuit, a short circuit to ground (0V), or a low supply voltage reaching the sensor.

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• Case IH Puma

1. 1

   Visually inspect the tractor's batteries and alternator for any signs of damage or accumulated debris, as a general low system voltage can trigger sensor faults.

2. 2

   Check the UCM fuses (e.g., F1 through F9) and HCU circuit breakers (e.g., F30) to ensure they are intact and receiving proper battery voltage.

3. 3

   Test the load side of the circuit breaker for battery voltage; if the voltage is low, the circuit breaker or battery connection may be at fault.

4. 4

   Inspect the wiring harness for the hitch position sensor to check for high resistance, an open circuit, or a short circuit to 0V/ground.

1. 1

   Inspect

   Turn off the tractor and inspect the rear hitch position sensor and its wiring harness for physical damage or disconnected pins.

2. 2

   Test

   Use a multimeter to check for high resistance or an open circuit between the battery/UCM and the sensor. Repair any damaged wiring or shorts to ground.

3. 3

   Check

   Check the circuit breakers and fuses supplying the UCM/HCU. If you detect low voltage on the load side of the circuit breaker, replace the circuit breaker.

4. 4

   Replace

   If the wiring and power supply are functioning correctly but the fault persists, replace the hitch position sensor itself.

5. 5

   Calibrate

   After replacing the sensor or repairing the circuit, you must calibrate the hitch position potentiometer via the tractor's display/UCM menu. The calibration procedure teaches the UCM the sensor's specific voltage values for the "fully lowered" and "fully raised" positions.

6. 6

   Verify

   Clear the fault codes and restart the vehicle to verify the repair.