How do I troubleshoot a faulty engine coolant temperature sensor on my Audi A2?

My Audi A2 has been running hot and I suspect that it may be due to a faulty engine coolant temperature sensor. How do I test and replace this sensor?

The first step in troubleshooting a faulty engine coolant temperature sensor is to ensure that it is actually the cause of your vehicle's heat issue. Use an OBD-II scanner to check for any error codes related to the sensor, and also check the sensor's reading against the actual coolant temperature using a thermometer. If the sensor reading is significantly different from the actual temperature, then it is likely faulty.