P0030 HO2S  engine's primary oxygen sensor malfunctioning Heater Control Circuit (Bank 1 Sensor 1)  the oxygen content of the car exhaust. All this information is then later sent to the engine control module so that it can adjust the fuel which is delivered to the car engine.

The heater circuit element inside the HO2S might be failed or damaged

The O2 sensor heater ground circuit may be opened

There can be some failure in the ECM

Open or short on O2 sensor heater B+ battery feed

Replace/Repair These Parts To Fix OBD Code P0030

 Then there's definitely some fault with the Sensor heaters. Get it checked and replace if needed.

Engine Control Module -A damaged Engine Control Module can cause a lot of issues. 

The check engine light would start appearing

With the O2 heater circuit not working the O2 sensor response time will be affected and the sensor will not respond to fuel and oxygen in the exhaust for the first 3 to 5 minutes of running or more

The ECM would be affected by the lack of response and the ability to control the fuel mixture and it will go into a fixed fuel mix until the problem is fixed

 Several problems can arise, but the most common out of them is the wiring being damaged by excessive heat from the exhaust. Make sure that the wiring is in good working condition has proper voltage and ground to the sensor before you start to replace the sensor

Make sure that the key is on and your car engine is turned off, then you can use a voltmeter to check for 12+ volts fused battery feed to the heater element.

If the resistance is infinite, then you must repair the open circuit

 The mechanic can reset the OBD-II code and then later you can always test drive your vehicle to insect if the engine warning light and code is returning back or not. If it comes back on, the mechanic should check both power and ground to the sensor, including inspecting the wiring and sensor.