Case IH t5B – Transmission/EDC or EMU: Reverse Polarity Of Engine Speed Sensor, Data Valid But Below Normal Range

The control module is receiving a valid signal from the engine speed sensor, but the electrical polarity is reversed (which can happen if wires are swapped, shorted, or the sensor fails internally) and the data falls below the expected operational range.

• MXM
• MXM 120
• MXM 130
• MXM 140
• MXM 155
• MXM 175
• MXM 190
• TM115 through TM190

1. 1

   Visually inspect the engine speed sensor, wiring harness, and connector for physical damage, melting, or corrosion.

2. 2

   Verify the wiring polarity at the sensor connector to ensure the two wires have not been de-pinned and swapped during a previous repair.

3. 3

   Check the sensor seating to ensure it is fully seated and properly gapped against the internal gear teeth, as a loose sensor can cause a weak signal.

4. 4

   Use a multimeter to check for continuity between the sensor connector and the ECU/EDC module, and test the sensor's resistance for internal failure.

1. 1

   Prepare tractor for repair

   Park the tractor on a level surface, turn off the engine, and disconnect the battery to prevent electrical shorts.

2. 2

   Locate sensor

   Locate the engine speed sensor on the engine block, flywheel bell housing, or transmission housing.

3. 3

   Disconnect sensor

   Disconnect the 2-pin electrical connector from the sensor.

4. 4

   Correct wiring polarity

   If the diagnostic checks revealed swapped wires in the harness connector, re-pin the connector to correct the polarity.

5. 5

   Remove retaining bolt

   If the sensor itself is faulty, remove the retaining bolt securing the sensor to the housing.

6. 6

   Remove old sensor

   Carefully pull the old inductive speed sensor out of the mounting hole.

7. 7

   Install new sensor

   Clean the mounting surface. Insert the new OEM engine speed sensor and tighten the retaining bolt.

8. 8

   Reconnect connector

   Reconnect the 2-pin electrical connector, ensuring the weather seal is intact.

9. 9

   Restore power

   Reconnect the battery and turn the key to the 'ON' position.

10. 10

    Clear fault codes

    Clear the stored fault codes from the 'H' menu / diagnostic display.

11. 11

    Verify operation and calibrate

    Start the engine and verify that the RPM/speedometer reads correctly. If necessary, perform a Transmission/EDC calibration setup procedure.