CLAAS Id7738h / 7738h (412 00) – ENG (A15): Temperature of cooled exhaust gases excessively high.

When this condition is detected, the system triggers a protective derate. The engine calculator reduces engine power by 20% per minute until it reaches 50% of its nominal power to prevent engine damage (power is recovered at the same rate of 20% per minute once the fault clears).

• Axion 810
• Axion 820
• Axion 830
• Axion 840
• Axion 850
• Arion 510
• Arion 530
• Arion 550
• Arion 620
• Arion 640
• Arion 650

1. 1

   Check the cooled exhaust gas temperature sensor (B221) for proper operation. Inspect the wiring harness and connectors linking to the B221 sensor for continuity, short-circuits, or open circuits.

2. 2

   Verify that the engine coolant level is sufficient.

3. 3

   Ensure the coolant thermostat is functioning and opening at the correct temperature.

4. 4

   Inspect the exhaust gas recycling (EGR) cooler for blockages, internal failure, or restricted flow.

1. 1

   Inspect Coolant System

   Check the coolant expansion tank. If the coolant level is low, top it up and pressure test the system to find any leaks.

2. 2

   Test the Thermostat

   If the coolant level is fine, verify the coolant thermostat is operating correctly. A stuck-closed thermostat will cause poor cooling of the EGR system.

3. 3

   Inspect the EGR Cooler

   Check the exhaust gas recycling cooler for soot blockages or internal coolant scaling that would prevent it from properly cooling the exhaust gases. Clean or replace the EGR cooler if it is clogged.

4. 4

   Test Sensor B221

   If the mechanical cooling components are functioning properly, test the B221 Cooled exhaust gas temperature sensor. Check its resistance and verify the wiring harness for any short-circuits to ground or open circuits.

5. 5

   Replace Sensor

   If the sensor is reading out of range or has failed internally, replace the B221 sensor and clear the fault codes.