Estimates Trouble Codes P0030

P0030: HO2S Heater Control Circuit (Bank 1, Sensor 1)

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What Is P0030?

Diagnostic Trouble Code P0030 is defined as “HO2S Heater Control Circuit (Bank 1, Sensor 1)”. It indicates a fault within the heater circuit in oxygen sensor Bank 1, Sensor 1.

For the vehicle engine to function properly, it should have a specific air-to-fuel ratio. The heated oxygen sensor (HO2S) detects the oxygen content in the exhaust gas. It sends this information to the engine control module (ECM), which uses this data to adjust the fuel delivered to the engine.

So what does error code P0030 mean?

Oxygen sensors need to be heated to work. So every heated O2 sensor has an internal heater that gets them to the right operating temperature (usually 600°F).

If the heating element fails, the oxygen sensors can’t accurately report the data to the Engine Control Module. This is when the ECM triggers the Check Engine Light and registers error code P0030.

Note: Other codes related to the HO2S include P0031, P0032, P0036, and P0037.

Common Symptoms

The P0030 code shows very few noticeable symptoms apart from a lit engine light

However, you can look out for the following signs for code P0030:

Illuminated Check Engine Light: If the heated oxygen sensor fails due to the malfunctioning heater element circuit, the combustion may suffer. So the ECM triggers error code P0030 and the engine light for immediate attention.

Decreased fuel performance: The heated oxygen sensor #1 measures the oxygen content in the exhaust gas and helps determine how to adjust the air-fuel ratio. So the combustion process suffers if there’s a malfunction in the O2 sensor circuit. As a result, you will experience increased fuel consumption and decreased fuel efficiency.

Failed emissions test: A bad O2 sensor won’t accurately monitor the exhaust ratio. So you’re likely to fail an emissions test with error code P0030.

Can I Still Drive?

DTC P0030 is a relatively drivable fault code. It usually doesn’t affect the engine performance apart from the Check Engine Light turning on. So, you can still drive your vehicle for a short distance if this code comes up.

However, if the problem stems from a wiring problem or ECM failure, the problem could be more serious. So you should get your vehicle to the mechanic for maintenance or DTC troubleshooting as soon as possible.

P0030 Causes

The P0030 code can be caused due to several factors, including:

  • Damage or failing heater circuit element inside H02S
  • Problem on the ground side of the O2 sensor heater circuit
  • Issues on the power side of the O2 sensor heater circuit
  • Bad O2 sensor heater element with open circuit
  • Higher resistance in the oxygen sensor elements 
  • Problems with the sensor connector wiring
  • ECM wiring or wiring harness problem
  • Blown fuse in the vehicle fuse box
  • Complete sensor failure
  • A failing ignition coil or coil pack (rare)
  • Malfunction in the ECM (rare)


Here’s how a mechanic carries out a fault code P0030 troubleshooting:

1. Your mechanic will start by connecting the engine to an OBD-II scanning tool. They’ll pull the other codes, capture freeze frame data, check why the engine light is on, and take a road test to see if the codes return.

2. Next, they’ll visually inspect the circuit wiring and the wiring harness and compare them with the vehicle’s wiring diagram. There could be exhaust heat damage, or the catalytic converter may malfunction. They’ll also check the control circuit connector and the heated oxygen sensor connector for cracks.

3. If the circuit wiring is OK, the next step is to check the voltage and ground of the sensor for continuity. Inspect the heated oxygen sensor fuse.

4. Using a voltmeter, your mechanic will verify that at least 12 volts are going from the battery to the O2 sensor heater. Replace the fuse if necessary.

If the voltmeter readings indicate that the battery is OK, then the problem might be with the ECM sensor. To check this, your mechanic will take the ground from the ECM and look for resistance. Infinite resistance means the ECM needs repairing.

If the ECM is working properly, the O2 sensor probably needs to be repaired. They’ll replace it with a new sensor if necessary and perform another maintenance road test.

Possible Repairs for P0030 & Costs

In most cases, the oxygen sensor heating element gets broken due to impact or age. In others, you may have to replace it with a new sensor.

Here are some other repairs that may be needed:

  • Replacing the faulty oxygen sensor
  • Repairing or replacing the oxygen sensor circuit wiring
  • Replacing any blown fuse (in the fuse box) for the oxygen sensor heater control circuit
  • Repairing any open or short circuit

If you have a bad upstream O2 sensor, you can expect to pay anywhere from $20 to $200 for a new oxygen sensor. To that, add $30 to $40 in labor charges.

2 FAQs on Code P0030

The following are answers to 2 common questions related to the P0030 error code:

1. What Does Bank 1 Sensor 1 Do?

The Bank 1 Sensor 1, or the pre-cat O2 sensor, is responsible for monitoring the oxygen content in the exhaust gas and providing an accurate voltage signal to the ECM.

Getting an accurate voltage signal is essential, as the ECM interprets this information for adjusting the air-fuel ratio.

The Bank 1 Sensor 1 is also known as the upstream O2 sensor or pre-cat 02 sensor. It’s located before the catalytic converter (on the exhaust manifold), on the side with cylinder #1.

Note: Your engine’s Bank 1 can be located on the driver or passenger side, depending on your engine configuration, but it’s always based on the cylinder #1 position. A Bank 2 sensor would be on the side with cylinder #2. Some engines (like an inline 4-cylinder) only have one bank. 

2. How Does the Heated Oxygen Sensor Work?

Every heated oxygen sensor has its own heater element circuit. The HO2S heater control circuit helps bring the sensor to the optimum operating temperature.

Once running, the sensor continually communicates with the ECM to determine if the fuel is burning too rich (not enough oxygen) or lean (too much oxygen) — based on measurements in the exhaust gas.

If the air-fuel ratio is rich, it will give out a voltage of 800-1000mV. If the air-fuel ratio is lean, it will generate an even smaller amount (100-200mV). Once this information reaches the ECM, it releases more or less fuel to balance the air-fuel mixture.

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