Error Code P0030 is defined as Heater Control Circuit B1S1 (Bank 1, Sensor 1), which indicates a heater control circuit malfunction. This refers to a problem with the heater element of the heater’s HO2 sensor.

One of the many tasks of the control module is to monitor how long it takes for the sensor to warm up and start transferring an ample signal. This error code gets triggered when it notices that that the sensor is taking too long to warm up.


For a vehicle’s engine to function properly, it requires a specified ratio of fuel and air. This ratio should be 14.7:1 (air:fuel). To maintain this ratio, the PCM (powertrain control module, also called as ECM) depends on the HO2 sensors, as the latter detects oxygen content inside the exhaust. The sensor is located next to the catalytic converter, and it works by detecting the concentration of oxygen in the exhaust gas.

This information is then passed to the PCM, which uses this information to set the right amount of fuel to be transported to the engine. A heated sensor comprises of a circuit dedicated to specifically operate the heater that warms up the O2 sensor, and it should perform this task quicker than the gasses of the exhaust can. Along with decreased emissions, this also cuts the time it takes for the engine to reach a closed loop.

Modern vehicles now use heated oxygen sensors, which bring a heating element that allows the sensor to reach the ideal temperature faster. This helps the PCM to send input signals much sooner, resulting in reduced emissions and precise fuel control. A series of relays energize the heater circuit which closes due to a cranked engine. The PCM checks the heater circuit and activates the Check Engine light if it spots a problem.

Common Symptoms

Aside from the illumination of the Check Engine light, common symptoms for this error code include:

  • O2 sensor response time affected
  • Unresponsive sensor (not responding to the fuel and oxygen for around 5 minutes of running time)
  • Lack of response affecting the ability of the PCM to control fuel mixture where it will head straight to a fixed fuel mix until problem gets solved
  • Poor fuel economy
  • Vehicle failing an emission test

Possible Causes

This error code is usually caused by problems in the oxygen sensor heater circuit or by the heater sensor itself. Some possible causes include:

  • Damaged or failed heater circuit element right inside H02S
  • Open oxygen sensor ground circuit heater
  • Problem on the ground side of Oxygen sensor heater circuit, or the power side.
  • Oxygen sensor elements has higher resistance
  • Oxygen sensor heater element with open circuit
  • Open or short Oxygen sensor heater’s B+ battery feed (which is usually a control circuit on some vehicles)

Many problems encountered with this code are wiring related, which is caused by the heat of the exhaust.

How to Check

You will need an OBD-II scanner to help determine the cause of the fault. Mechanics usually reset the code and the conduct a test drive to see whether the Check Engine light is on and code returns. If the code comes back, then the mechanic needs to check the power and the ground of the sensor.

Mechanics use them in almost everything engine related. In this case, they usually start with a visual inspection to test the wiring and connections between the heater circuit and the sensor heating element.

How to Fix

In many cases, the oxygen sensor heater element gets broken due to impact or age. Bear this in mind when conducting an inspection of the Bank 1 oxygen sensor. Fix any broken wiring from contact with the exhaust.

If it’s the oxygen sensor itself that is damaged, then it needs to be replaced. If visual inspection shows no obvious problem, the faulty heater scan tool may show whether the code is presently happening. If the scan tool records 0 amps on the Bank 1, 1 heater element, then there’s a good chance of an open circuit. To fix this, check for any blown fuses and disconnect the oxygen sensor connector.

Using the voltmeter, with the engine off, check whether there’s a 12V fused battery feed to the heater element. If you see no voltage, then repair the short or open in the B+ feed circuit. Remember to replace the blown fuse from the short.

If you see that the B+ battery feed is still intact, then remove the ground circuit (control) from the wiring connector of the PCM and check the circuit for resistance. Fix the circuit open should you determine infinite resistance. Should the circuit of the control check out, then there’s a good chance it’s a case of a bad oxygen sensor. Replace the sensor and then re-check.

Never assume that the heater oxygen sensor is already bad and needs replacement. Make sure you check all related wiring and connectors closely.

Each side of the connector must be thoroughly checked to make sure the connector is not damaged.

Mechanics must ensure 12V to the sensor and ground must be good.