CLAAS Id772Eh / 772Eh (110 17) – ENG (A15): Engine coolant temperature is slightly low

The engine temperature has not risen to the normal operating range within the expected timeframe. The engine will continue to run normally. This condition is most commonly caused by a thermostat that is stuck open, preventing the engine from warming up, or a faulty temperature sensor providing an inaccurate reading.

• Axion 800 series
• Axion 810
• Axion 820
• Axion 830
• Axion 840
• Axion 850
• Axion 900 series
• Axion 960
• Arion 400 series
• Arion 410
• Arion 430
• Arion 500 series
• Arion 530
• Arion 550
• Arion 600 series
• Arion 620
• Arion 640
• Arion 650
• Jaguar
• Lexion

1. 1

   Inspect the engine cooling circuit for adequate coolant levels, leaks, and verify if the thermostat is stuck open (which overcools the engine).

2. 2

   Check the engine coolant temperature sensor (B45) physical condition, wiring harness, and connector.

3. 3

   Verify the engine module ENG (A15) is receiving the signal and check for harness continuity between the B45 sensor and the ECU.

1. 1

   Visual Inspection & Fluid Check

   Verify the coolant level in the expansion tank. Top up if necessary and inspect the cooling circuit for any visible leaks.

2. 2

   Thermostat Evaluation

   Start the engine from cold and monitor the temperature of the radiator hoses. If the upper radiator hose gets warm immediately rather than staying cool until the engine reaches operating temperature, the thermostat is stuck open and must be replaced.

3. 3

   Sensor Testing (B45)

   If the engine is physically reaching operating temperature but the code persists, test the B45 Coolant Temperature Sensor. Perform a power check at the sensor connector and a resistance check on the sensor across different temperatures to ensure it scales correctly according to OEM specs.

4. 4

   Harness Check

   Inspect the wiring harness between the B45 coolant temperature sensor and the ENG (A15) module for shorts to ground, breaks, or corrosion.

5. 5

   Clear Codes

   After replacing the faulty thermostat or sensor, clear the fault codes from the ENG (A15) module and test-run the machine to ensure it reaches and maintains normal operating temperature without triggering the code.