Diagnostic trouble code (DTC) information

Condition 

Fig 1: Identifying Engine Coolant Temperature (ECT) Sensor

Courtesy of VOLVO CARS OF NORTH AMERICA.

Diagnostic trouble code (DTC) ECM-200A is stored if the engine control module (ECM) registers that the engine coolant temperature (ECT) does not increase a certain number of degrees (depending on outer temperature within a certain time of starting.

Substitute Value 

• if the temperature sensor in the mass air flow (MAF) sensor is OK it is used as the start temperature. Otherwise the value is set at +20°C (68°F)
• after starting the engine coolant temperature (ECT) is calculated theoretically
• engine cooling fan (FC) at low-speed.

Possible Source 

Faulty signal 

• contact resistance in connector
• defective thermostat
• defective engine coolant temperature (ECT) sensor.

Fault symptom[s] 

• difficult to start when cold
• driveability problems during warm-up cycle
• engine cooling fan (FC) operates constantly.