John Deere 000109.04 – ECU: Coolant Pressure Is Low

The Engine Control Unit (ECU) has detected that the engine's coolant pressure is below the normal operating range. This condition can trigger an engine power derate to prevent potential damage from overheating.

• 6E
• 6M
• 6R
• 7R
• 8R
• 8RT
• 8RX
• 9R
• 9RT
• 9RX
• 210G
• 250G
• 290G
• 300G
• 350G
• 380G
• 470G
• 524K
• 544K
• 624K
• 644K
• 524L
• 544L
• 624L
• 644L
• 724L
• 744L
• E-Series Articulated Dump Trucks
• P-Series Articulated Dump Trucks
• E-Series Dozers
• P-Series Dozers

1. 1

   Visually inspect the entire cooling system for obvious signs of leaks, paying close attention to hoses, the radiator, the water pump, and loose or damaged hose clamps.

2. 2

   Check the coolant level in the de-aeration tank and recovery tank. Top off with the recommended John Deere coolant if the level is low.

3. 3

   Pressure test the radiator cap using a tester to the specification listed for your machine (typically around 10 psi or 0.7 bar). Replace the cap if it fails to hold pressure for at least 10 seconds.

4. 4

   Pressure test the cooling system with the engine cool. Observe the gauge for any drop in pressure; if no external leaks are visible but pressure drops, it could signify an internal engine leak which requires immediate attention from a qualified technician.

1. 1

   Locate the sensor

   Locate the coolant pressure sensor on the engine block, which is often situated near the coolant temperature sensor and AC compressor.

2. 2

   Prepare for coolant loss

   Place a drain pan under the sensor location. Partially drain the cooling system to a level below the sensor to minimize spillage during removal.

3. 3

   Disconnect electrical connector

   Disengage the locking tab on the sensor's electrical connector and unplug it.

4. 4

   Remove the old sensor

   Using an appropriately sized socket (typically 7/8 inch), carefully unscrew and remove the faulty coolant pressure sensor.

5. 5

   Install the new sensor

   Ensure the new sensor has an O-ring or appropriate sealing mechanism. Thread the new sensor in by hand to avoid cross-threading, then tighten it to the manufacturer's specified torque. Do not overtighten.

6. 6

   Reconnect electrical connector

   Securely plug the electrical connector back onto the new sensor.

7. 7

   Refill and bleed the cooling system

   Top off the cooling system with the correct coolant mixture. Start the engine and let it run to purge any air from the system, then re-check the coolant level and top off as necessary.

8. 8

   Clear fault codes

   Clear the active fault code from the machine's diagnostic system.