Case IH tE4 – PCU (Power Control Unit) / Transmission Controller or Engine Control Module (ECM): Fan speed signal error

The control module is not receiving a valid RPM signal from the engine's cooling fan speed sensor, or the signal is out of the expected parameters.

• MXM
• MXM120
• MXM130
• MXM140
• MXM155
• MXM175
• MXM190

1. 1

   Inspect the wiring loom from the viscous fan around the radiator cowl for chafing, melted insulation, or physical damage.

2. 2

   Test the sensor connector for a proper 5-volt reference signal to ensure there is no short to ground.

3. 3

   Inspect the sensor target rivet or nut on the fan impeller to ensure it is intact, free of heavy debris, and the sensor gap is correct.

4. 4

   Test the fan speed sensor to verify it outputs a frequency signal when the fan is manually rotated or while the engine is running.

1. 1

   Disconnect Battery

   Always disconnect the battery before servicing ECU-linked electrical components.

2. 2

   Repair Wiring

   If a short or break is found in the loom near the radiator cowl, splice and heat-shrink the damaged wires, then re-route the loom away from vibration points.

3. 3

   Replace the Fan Speed Sensor

   If the wiring is intact but no signal is generated, unbolt the fan speed sensor from its mounting bracket near the fan impeller, disconnect the pigtail, and install the new sensor. Adjust the sensor gap according to the service manual specifications.

4. 4

   Replace the Viscous Fan Clutch

   If the sensor and wiring check out perfectly, the internal PWM solenoid or the sensor ring inside the viscous fan unit may have failed. Remove the fan shroud and drive belts. Unbolt the viscous fan clutch assembly from the water pump/pulley flange. Transfer the plastic fan blades to the new viscous drive clutch. Mount the new assembly, reconnect the 5-pin electrical connector, and reinstall the belts and shroud.

5. 5

   Clear Codes

   Reconnect the battery and use a diagnostic tool (or the tractor's onboard diagnostic menu) to clear the tE4 code and verify the fan RPM registers on the dash/monitor.