Massey Ferguson E109.04 – Engine Control Unit (ECU): Coolant Pressure Sensor Signal Voltage Low

The Engine Control Unit has detected that the measured voltage signal coming from the coolant pressure sensor is below the normal operating range, typically indicating a short circuit to ground in the sensor wiring or an internal failure of the sensor itself.

• 7616
• 5612
• 7622
• Interim Tier 4 (2012-2015)
• 7614
• 5611
• 7615
• 5610
• 5613
• 7620
• 5609
• 7618
• 5608
• 7619
• 7626
• 7624
• 4707
• 4708
• 4709
• 4710
• 5710SL
• 5711SL
• 5712SL
• 5713SL
• 7714
• 7715
• 7715S
• 7716
• 7716S
• 7718
• 7718S
• 7719
• 7720
• 7720S
• 7722
• 7722S
• 7724
• 7724S
• 7726
• 7726S

1. 1

   Check the Error Log using the WinEEM3s/EEM4 Service Tool to confirm the code is active

2. 2

   Inspect the wiring harness leading to the coolant pressure sensor for chafed insulation, pinched wires, or a short circuit to ground

3. 3

   Verify sensor operation by temporarily plugging in a known-good (or new) coolant pressure sensor to see if the fault clears

1. 1

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

2. 2

   Locate the coolant pressure sensor on the engine block's cooling circuit.

3. 3

   Disconnect the 3-pin electrical connector from the sensor. Inspect the connector pins for corrosion, moisture, or damage.

4. 4

   Using a multimeter, verify that the wiring harness is not shorted to ground.

5. 5

   If the wiring is intact, relieve any residual pressure in the cooling system by carefully loosening the radiator/expansion tank cap (ensure the engine is cool).

6. 6

   Unthread the defective coolant pressure sensor and quickly install the replacement sensor to minimize coolant loss.

7. 7

   Reconnect the electrical harness.

8. 8

   Reconnect the battery, start the engine, and use the diagnostic service tool to clear the stored E109.04 / 00109.04 fault code.

9. 9

   Run the engine up to operating temperature and verify that the warning lamp remains off and no leaks are present.