Massey Ferguson 109.04 – EEM4 (Electronic Engine Management 4): Coolant Pressure Sensor Signal Voltage Low

The voltage signal returning from the engine coolant pressure sensor to the controller has dropped below the normal operating range. This typically indicates a short circuit to ground in the sensor's wiring harness, or an internal failure of the sensor itself.

• 7724S
• 5712SL
• 7722
• 7722S
• 5713SL
• 7720S
• 7716
• 7718
• T4
• 7715
• 5710SL
• 7726
• 7726S
• 5711SL
• 7718S
• 7719
• 7714
• 7716S
• 7720
• Tier 4 (2015-2021)
• 7715S
• 7724
• 4707
• 4708
• 4709
• 4710
• 5608
• 5609
• 5610
• 5611
• 5612
• 5613
• 7614
• 7615
• 7616
• 7618
• 7619
• 7620
• 7622
• 7624
• 7626
• 5700SL Series
• 7700 Series
• 8600 Series
• 8700 Series

1. 1

   Connect a diagnostic service tool (like WinEEM4) to confirm the fault is active and save the error log.

2. 2

   Locate the coolant pressure sensor (B16 or B3M) and inspect the wiring harness between the sensor and the ECU for chafing, bare wires, or pinch points that could cause a short to ground.

3. 3

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

4. 4

   With the sensor unplugged and the key ON, check the reference voltage at the connector. It should read 5Vdc between the analog input pin and the ground pin. If missing or shorted, the issue is in the wiring harness or the ECU.

5. 5

   If the wiring and reference voltage test good, temporarily connect a known-good coolant pressure sensor to see if the fault clears.

1. 1

   Power Down

   Turn off the tractor and disconnect the battery ground cable to prevent electrical spikes.

2. 2

   Locate the Sensor

   The coolant pressure sensor is typically located on the engine's cooling circuit. Depending on the specific engine displacement (e.g., 84 or 98 series engines), it may be installed directly in the coolant expansion tank or near the thermostat housing/coolant pump.

3. 3

   Relieve Pressure

   If the engine is warm, allow it to cool completely. Slowly loosen the expansion tank cap to relieve any residual pressure in the cooling system.

4. 4

   Remove the Sensor

   Disconnect the electrical connector. Use a wrench to unthread the defective coolant pressure sensor from its port. Have a rag ready to catch any minor coolant spillage.

5. 5

   Install the New Sensor

   Thread the new OEM sensor into the port. Tighten to the manufacturer's specified torque (do not over-tighten, as it threads into plastic or cast aluminum depending on the location).

6. 6

   Reconnect and Clear Codes

   Reconnect the electrical harness. Reconnect the battery, turn the key ON, and use the diagnostic service tool to clear the stored 00109.04 / SPN 109 FMI 4 fault code.

7. 7

   Test Run

   Start the engine, check for coolant leaks at the sensor fitting, and verify that the warning lamp remains off.