Case IH 19405 – Engine Control Unit (ECU): Monitoring of high pressure in sea water circuit, OR high coolant pressure at inlet of main cooling pump

The engine's control system has detected that the pressure in the cooling circuit (either the standard engine coolant circuit or the raw sea water circuit) has exceeded the maximum allowable threshold. This can be caused by a genuine overpressure situation (e.g., a blockage in the cooling system, a stuck thermostat, or a failing water pump) or a false reading due to a faulty pressure sensor or wiring harness short.

• Tier 4b
• T7 series
• Puma
• Optum
• Magnum
• FPT Marine and Industrial engines

1. 1

   Verify the sensor reading using a diagnostic tool (like CNH EST) and compare it against a mechanical pressure gauge to determine if the pressure is actually high or if the sensor is faulty.

2. 2

   Inspect the wiring harness between the coolant pressure sensor and the ECU for chafing, breaks, or a short circuit to ground/external voltage.

3. 3

   Disconnect the sensor and check the connector for moisture or coolant migration, a known issue on FPT engines.

4. 4

   If the sensor reads accurately, inspect the physical cooling system for a genuine overpressure cause, such as a stuck-closed thermostat, a blocked radiator/heat exchanger, or a malfunctioning water pump.

1. 1

   Disconnect Power

   Turn off the machine and disconnect the negative battery terminal to prevent electrical spikes.

2. 2

   Locate the Sensor

   Locate the coolant pressure sensor (often mounted on the coolant expansion tank, near the water pump inlet, or on the sea water circuit piping depending on the exact engine application).

3. 3

   Inspect and Clean

   Disconnect the sensor plug. If the plug is wet or corroded, clean it thoroughly with electrical contact cleaner. If the yellow weather seal is compromised, it must be replaced.

4. 4

   Replace the Sensor

   If the wiring tests good but the sensor is outputting out-of-range voltages, unscrew the faulty sensor. Note: Ensure the cooling system is depressurized and cool before removing the sensor to prevent injury. Install the new sensor and tighten to OEM torque specs.

5. 5

   Reassemble and Clear Codes

   Reconnect the wiring harness and the battery. Use a diagnostic tool to clear the 19405 fault code from the ECU memory.

6. 6

   Test Run

   Start the engine and bring it up to operating temperature. Monitor the live coolant pressure data to ensure it remains within the normal operating range and verify that the fault code does not return.