Case IH U57 – Transmission ECU: Engine Torque/RPM Sensor Short To Ground

The ECU is detecting zero or near-zero voltage on the sensor's signal circuit, indicating that the electrical current is escaping directly to the chassis ground. This is typically caused by a pinched wire, chafed harness insulation, or an internal short within the sensor itself.

• MXM
• MXM 120
• MXM 130
• MXM 140
• MXM 155
• MXM 175
• MXM 190

1. 1

   Trace the wiring harness from the Engine Torque/RPM Sensor back to the Transmission ECU for chafed insulation, pinched wires, or rubbing against the chassis.

2. 2

   Disconnect the sensor's electrical connector and use a multimeter to check for continuity to ground on the signal wire (if short disappears, sensor is faulty; if it remains, harness is faulty).

3. 3

   Ensure the Engine Torque/RPM sensor has not been accidentally swapped with the transmission mid-speed or output speed sensors during previous maintenance.

4. 4

   Inspect the sensor mounting area at the flywheel damper for physical damage or heavy debris buildup that could interfere with the magnetic field.

1. 1

   Preparation

   Park the tractor on a level surface, apply the parking brake, turn off the engine, and disconnect the battery to prevent electrical spikes.

2. 2

   Locate the Sensor

   Locate the Engine Torque/RPM Sensor, which is mounted on the bell housing/flywheel damper area.

3. 3

   Disconnect

   Unplug the electrical connector from the sensor.

4. 4

   Remove the Sensor

   Remove the retaining bolt(s) securing the sensor to the housing. Carefully pull the sensor straight out. (Twisting may be required if the O-ring is stuck).

5. 5

   Install the New Sensor

   Lubricate the O-ring on the new sensor with a small amount of clean oil. Insert the sensor into the housing and install the retaining bolt. Tighten to the OEM specified torque.

6. 6

   Reconnect

   Plug the electrical connector back into the sensor, ensuring the locking tab clicks into place.

7. 7

   Clear Codes & Calibrate

   Reconnect the battery and start the tractor. Access the tractor's 'H-Menu' (Diagnostic Menu) or use the CNH Electronic Service Tool to clear the U57 fault code.

8. 8

   Test

   Test drive the tractor to ensure smooth shifting and verify that the code does not return. A transmission/clutch calibration may be required if shift quality has deteriorated.