Case IH t4A – Digital Instrument Cluster (EIC) / Engine Controller (EDC): Coolant Temperature Sensor, Grounded Or Current Above Normal Range

The control module is detecting that the signal voltage from the engine coolant temperature sensor has dropped to zero (shorted to ground) or the current draw is exceeding the normal operating parameters. This usually points to a chafed wire touching the chassis, a melted connector, or an internally shorted sensor.

• MXM
• MXM 120
• MXM 130
• MXM 140
• MXM 155
• MXM 175
• MXM 190
• TM120
• TM190
• Magnum
• Steiger
• Puma
• Farmall
• C50
• C90
• CX50
• CX100

1. 1

   Turn the key OFF and disconnect the battery to prevent false readings or module damage.

2. 2

   Inspect the wiring harness routing from the coolant temperature sensor to the ECU/EIC for rubbed-through insulation, pinched wires, or melted loom.

3. 3

   Disconnect the harness connector at the coolant temperature sensor and at the ECU/EIC to isolate the circuit.

4. 4

   Test for a short to ground: Set a multimeter to measure resistance (Ohms). Place the black lead on a clean chassis ground and probe the sensor signal wire pin on the harness with the red lead. Continuity indicates a shorted wire; infinite resistance (OL) indicates the wiring is likely good.

5. 5

   Test the sensor: If the wiring tests good, measure the resistance across the pins of the coolant temperature sensor itself. A reading near zero ohms indicates the sensor is internally shorted.

1. 1

   Trace harness

   If the wiring is shorted: Trace the harness to locate the exact point of the short.

2. 2

   Remove damaged wire

   Cut out the damaged section of the wire.

3. 3

   Splice new wire

   Splice in a new section of wire using a harness repair kit (use proper crimps and heat-shrink tubing to seal out moisture).

4. 4

   Re-loom harness

   Re-loom the harness and secure it away from hot or vibrating engine components.

5. 5

   Depressurize cooling system

   If the sensor is faulty: Ensure the engine is cool and depressurize the cooling system by slowly loosening the radiator cap.

6. 6

   Drain coolant

   Drain a small amount of coolant from the radiator petcock to bring the fluid level below the sensor port (this prevents a mess).

7. 7

   Disconnect sensor

   Disconnect the electrical connector from the sensor.

8. 8

   Remove old sensor

   Unthread the old coolant temperature sensor from the engine block/thermostat housing.

9. 9

   Install new sensor

   Thread in the new sensor (apply thread sealant if it does not come pre-applied) and tighten to OEM torque specs.

10. 10

    Reconnect connector

    Reconnect the electrical connector.

11. 11

    Top off coolant

    Top off the engine coolant.

12. 12

    Verify repair

    Reconnect the battery, turn the key ON, and clear the fault codes. Start the engine and verify the temperature gauge reads correctly and the t4A code does not return.