John Deere 109.01 – Engine Control Unit (ECU): The Coolant Pressure Is Low

The coolant pressure within the engine has dropped significantly below a defined operational threshold. When this code is active, the machine will typically enter a derate mode where engine power is limited to protect the engine from overheating or catastrophic failure.

• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 9470RT
• 9520RT
• 9570RT

1. 1

   Check coolant level to ensure it is filled to the proper specification

2. 2

   Inspect the pressure cap (sealed lid/radiator cap) and the sealing surfaces in the cooling system for damage or wear

3. 3

   Inspect the entire cooling system (hoses, radiator, water pump) for visible coolant leaks

4. 4

   Use a cooling system pressure tester to verify the system's integrity and ensure it can hold pressure

1. 1

   Address Leaks

   If the pressure test reveals a drop in pressure, locate and seal any leaks in the cooling system.

2. 2

   Replace the Pressure Cap

   If the sealed lid fails the pressure test or shows degraded rubber seals, replace it.

3. 3

   Inspect/Replace the Coolant Pump

   If the system holds pressure but circulation is poor, inspect the coolant pump (water pump) for internal failure and replace it if faulty.

4. 4

   Replace the Coolant Pressure Sensor

   If the system is mechanically sound, holds pressure, and has no leaks, the sensor itself may be sending a false 'Extremely Low' signal. Replace the coolant pressure sensor.

5. 5

   Verify Repair

   Refill the coolant, bleed the system of air, and thoroughly check the system while running to ensure coolant pressure is maintained within operational specifications.

6. 6

   Clear Codes

   Cycle power to the tractor (turn the ignition key to the off position and back on) to see if the code clears and engine power is restored.