John Deere 109.17 – Engine Control Unit (ECU): The Coolant Pressure Is Low

The engine's coolant pressure has dropped slightly below the minimum threshold programmed into the control unit. While it is a slightly low warning, it can lead to engine power limitation to protect the engine from overheating or damage.

• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 6R Series
• 6250R
• 7R Series
• 7200R
• 7310R
• 8R/8RT Series
• 8245R
• 8310RT
• 8400R
• 9R/9RT/9RX Series
• S-Series
• S650
• S670
• S680
• S690
• 7000 Series
• 8000 Series
• 7180
• 7380
• 7780
• 8100
• 8600
• 7760
• CP690
• CS690
• R4038
• R4044
• R4060

1. 1

   Visually inspect all components of the cooling system, including the radiator, hoses, and water pump, for visible coolant leaks.

2. 2

   Inspect the radiator pressure cap and its sealing gasket for damage or inability to hold pressure.

3. 3

   Conduct a detailed manual pressure test on the cooling system to identify any drop in pressure and pinpoint hidden leaks.

4. 4

   If the system holds pressure mechanically, inspect the coolant pressure sensor and its wiring harness for shorts to ground, open circuits, or corrosion at the connector.

1. 1

   Cool Down

   Turn off the engine and allow the machine to cool down completely to avoid burn hazards from pressurized coolant.

2. 2

   Test/Replace the Pressure Cap

   Remove the pressure cap and test it with a cap tester. If it fails to hold its rated pressure, replace it.

3. 3

   Address Mechanical Leaks

   If the manual pressure test reveals leaks in the hoses, radiator, or water pump, repair or replace the defective parts.

4. 4

   Replace the Coolant Pressure Sensor

   If no mechanical leaks are found and the system holds pressure normally with a manual gauge, the coolant pressure sensor has likely failed. Disconnect the wiring harness, unthread the old sensor, install the new sensor, and reconnect the harness.

5. 5

   Refill and Bleed

   Top off the coolant to the appropriate level using John Deere-approved coolant.

6. 6

   System Reevaluation

   Clear the ECU fault codes, start the engine, and bring it up to operating temperature. Reevaluate the system to ensure the code does not return and the machine meets operational specifications.