Case IH P59 – Engine Control Unit (ECU) / Electronic Management Unit (EMU): Crankshaft Speed Sensor, Shorted To Low Source

Fault code T59 (190-4) indicates that the Crankshaft Speed Sensor circuit is shorted to a low voltage source (ground). The control module is detecting a voltage signal from the magnetic pickup sensor that falls below the normal operating range. This prevents the computer from accurately tracking how fast the crankshaft is spinning, which is critical for proper fuel injection timing and engine operation.

• MXM
• Case IH MXM Series (MXM 120, 130, 140, 155, 175, 190)
• Case IH Maxxum Series (100, 110, 115, 120, 125, 130, 135, 140, 145, 150)
• Case IH Puma Series
• Case IH Farmall and JX Series (JX90, JX95)

1. 1

   Visually inspect the wiring harness routing from the crankshaft speed sensor to the ECU for rubbed-through insulation, melted wires, or pinched areas causing a short to ground.

2. 2

   Disconnect the sensor and inspect the connector pins for corrosion, moisture, or damage.

3. 3

   Verify the gap between the sensor tip and the flywheel teeth is within factory specifications (typically 0.5mm to 2.0mm).

4. 4

   Use a multimeter to test the sensor wiring harness back to the ECU for continuity to ground to confirm if the harness is shorted.

1. 1

   Locate the Sensor

   Find the crankshaft speed sensor, which is typically mounted on the side of the engine block near the flywheel housing.

2. 2

   Disconnect Power

   Turn the key switch to the "OFF" position and disconnect the battery ground cable to prevent electrical spikes.

3. 3

   Remove the Sensor

   Unplug the electrical connector. Remove the retaining bolt holding the sensor in place and pull the sensor straight out of the block.

4. 4

   Clean the Port

   Thoroughly clean the mounting surface and the sensor port to ensure no debris falls into the flywheel housing and that the new sensor will seat perfectly flat.

5. 5

   Install the New Sensor

   Insert the replacement sensor. If your engine requires manual gapping, set the gap to the flywheel teeth as per your specific engine's spec. Tighten the retaining bolt.

6. 6

   Reconnect

   Plug the electrical connector back into the sensor and reconnect the battery.

7. 7

   Clear Codes and Calibrate

   Turn the key switch to the "ON" position. Clear the stored fault codes. On MXM/TM series tractors, you may need to run the Transmission/EDC Calibration Set Up Procedure (setting engine speed to 1200 ERPM) to ensure the system recognizes the repaired circuit.