CLAAS 7F33h – ECM: Coolant Temperature Sensor Disconnection

The Engine Control Module (ECM) has detected a disconnection, open circuit, or short circuit in the engine coolant temperature (ECT) sensor circuit. The ECM relies on this sensor to monitor coolant temperature and adjust fuel injection, ignition timing, and cooling fan operation. A disconnection means the ECM receives no signal or an implausible signal, which can compromise engine efficiency and temperature management.

• Arion
• Lexion
• Jaguar
• Tucano
• Xerion

1. 1

   Visually inspect the coolant temperature sensor, electrical connector, and wiring harness for damage, corrosion, loose connections, breaks, or chafing.

2. 2

   Check the engine coolant level, as low coolant can cause incorrect sensor readings even if the sensor is functioning correctly.

3. 3

   Test the sensor's resistance with a multimeter (should be around 2000 ohms when cold and decrease as it warms up; infinite resistance indicates an open circuit).

4. 4

   Test the circuit voltage with the ignition on (engine off) to verify a 5-volt reference voltage at the connector and a solid ground connection.

1. 1

   Ensure safety and prep

   Park the machine on a level surface, turn off the engine, allow it to cool completely to avoid burns, and disconnect the battery.

2. 2

   Locate the sensor

   Find the coolant temperature sensor, typically screwed into the engine block, cylinder head, or near the thermostat housing.

3. 3

   Prepare for coolant loss

   Place a drain pan under the sensor area and partially drain the cooling system to a level below the sensor to minimize coolant loss.

4. 4

   Remove the old sensor

   Disconnect the electrical connector and carefully unscrew the old sensor from its housing using an appropriate wrench.

5. 5

   Install the new sensor

   Clean the threads and sealing surface on the engine. Install the new sensor and tighten to the manufacturer's specified torque without overtightening.

6. 6

   Reconnect and refill

   Reconnect the electrical connector and refill the cooling system with the correct type of coolant to the proper level.

7. 7

   Perform final checks

   Reconnect the battery, start the engine, check for leaks around the sensor, and clear the fault code using a diagnostic tool.