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P0030 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.


P0030: Oxygen O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1)

This article discusses what the P0030 engine error means, its symptoms, causes and how to have this engine error resolved.


Fault code DTC P0030 refers to the malfunctioning of the engine’s oxygen sensor. The engine’s oxygen sensor (HO2S), which is located in the exhaust chute of the car is responsible for estimating the ratio of oxygen in the exhaust that is being emitted by the car. For the smooth functioning of the engine, it is important that the engine operates at a fixed air-fuel ratio


. The oxygen sensor transmits this information regarding the oxygen levels in the exhaust to the Engine’s control module (ECM). ECM is the computer-based control unit that regulates the engine’s fuel consumption after receiving information about oxygen levels. The oxygen sensor is connected to a circuit specifically designated for heating the oxygen sensor. This heating up of the oxygen sensor allows the sensor to transport information faster, hence improving the ECM’s efficiency in regulating fuel supply, also known as the closing loop. A shorter turnaround time for closing the loop means lower levels of emissions. 


The fault code P0030 can be triggered due to various reasons related to connectors, wires and switches. Following are the most common causes of P0030:

– A fault in the heater’s circuit element (element has high resistance or an open circuit)

– Permanently damaged heater circuit

– Problem with the power side or the ground side of the oxygen sensor’s heater circuit

– The heater’s ground circuit is damaged or problematic

ECM wiring issues

– Complete sensor failure

It may also be the case that the ECM is faulty. However, this is not a common occurrence. 


The most prominent symptom of the fault code P0030 is the illuminated ‘check engine light’ icon on your dashboard. You may also experience reduced fuel economy and delayed timing of the closing loop. If you take an emissions test, your car is most likely to fail the test in the presence of P0030. 



There are various cell phone applications and car diagnostic scanners in the market that allow you to scan your car’s error codes. Examples include the TOAD-Total Auto Diagnostics app, Innova 3160g, Foxwell NT604 Elite etc. After you have detected that your car has a P0030 error, you can manually inspect the Bank 1 oxygen sensor, located right next to the catalytic converter. You need to check the following in the oxygen sensor:

– Electrical connectors should be intact and should not show a sign of burns or fusing

– Wire Harnesses should be intact

– Metal taps should be screwed in properly

If you detect any damage in any of these components, you will need to replace bank 1 sensor 1 (the oxygen sensor). Replacing the oxygen sensor, however, should be the last resort and it is always best to have your car examined by a professional car mechanic before going ahead with replacement of the sensor– keep in mind that sometimes a fault may not be traceable through visible examination alone. In case there is no visible damage observed, then you will have to consult a mechanic or technician to fix your car.

Professional Diagnosis

The mechanic will use an OBD-II scanner to check for the fault code. Once it is determined that P0030 exists, the mechanic will take the following steps:

– The mechanic will try resetting the code and test drive the car to check if the code had appeared erroneously. 

If the malfunction lamp lights up again, after resetting the code, the mechanic will then check the voltage and the ground of the sensor with the help of a voltmeter. With no problems detected with the ground of the sensor, the mechanic will check the voltage supply to the heater. If the voltage supply is less than 12 volts, then the battery feed may be replaced.

– If the volt inspection results in the battery show no worrying signs, then the mechanic will be shifting focus towards the ECM – there might be a problem with the ECM sensor. If the resistance levels on the circuit are infinite, that would call for a replacement of the ECM – which is a rare phenomenon. 

– If all of the above issues are ruled out and even the ECM is not faulty, then the Bank1 Sensor 1 (AKA- Oxygen sensor) needs to be replaced.

Common diagnostic mistakes

– Mechanics may skip the step of scanning and double-checking the code. This often leads to misinterpretation of the problem. 

– While checking for voltage supply to the heater circuit, the key must be in the ignition. Skipping this prerequisite can lead to an incorrect diagnosis

– It is also equally important to verify that the ground to the heater circuit is intact

– Both sides of the connectors need to be checked for damage

– Don’t skip the ‘verify and reset step’ as the error code might be showing temporarily due to the car having travelled over 100,000 miles. 

How serious is P0030?

The P0030 is nothing like a life-threatening kind of situation for your car. You can still continue to drive your car. However, it is best to have the issue resolved at the earliest opportunity in order to avoid excessive fuel consumption, less efficient engine performance, or possible damage to other engine and exhaust components of the vehicle

How to avoid P0030?

It is rather difficult to avoid situations where there is a chance of P0030 arising because sometimes something as small as bump in the road can cause damage to the circuit wiring or to other parts of the oxygen sensor. However, if company advised maintenance protocols are followed regularly, it can help reduce the occurrence of the P0030 fault code. 


If not fixed in time, P0030 can eventually lead to sensor loop failure – not to mention the excessive amounts of exhaust released into the atmosphere. Other engine and exhaust parts can be damaged, too. Hence, it is ideal to have your car checked as soon as possible to avoid any irreparable damage. 

P0030 Code – What Does It Mean & How To Fix It