P0031 Error Code: An In-depth Analysis of Causes, Symptoms, and Fixes

Automotive trouble codes, also known as onboard diagnostic codes, are registered on vehicles manufactured from 1996 and upwards whenever the PCM detects a fault on the system.

These fault codes help car owners and mechanics to identify the causes of a vehicle malfunction and possible ways of fixing it. But before fixing the registered fault, you need to understand what the code means.

P0031 is one of the thousand trouble codes that can be logged on a car and retrieved with an OBDII scan tool. This article explains everything you need to know about code P0031.

Let’s keep the dice rolling!


Code P0031 Definition

Here you go with the definitions of some codes for easy and better understanding.

  • Code P0031 stands for H02S heater control low [bank 1 sensor 1].
  • SubariP0031: defective Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1
  • Generic P0031: Oxygen Sensor Heater Control Circuit Low Bank 1 Sensor 1
  • Nissan P0031: Heated oxygen sensor (HO2S) 1 Bank 1 – low heater voltage

What Does P0031 Mean?

Whenever this code is registered on your car computer, it means the engine control module ECM detects a low voltage on the heated 02 sensors. This low voltage is a result of a malfunctioning oxygen sensor or issues with the heater element.

The function of the heater element is to enable the sensor to start working once the engine is turned on. The sensor reads the oxygen in the exhaust system and forwards the data to the car onboard computer.

The onboard computer works with the data delivered by the 02 sensors to regulate the air/fuel mixture ratio delivered to the engine during the combustion cycle. While the car computer depends on the sensor, it also relies on the hot exhaust gas to heat up and generate accurate data.

The heater element does the calculation as the engine is heating up. Once the onboard computer receives data from sensor 1, it adjusts the air/fuel mixture ratio based on the readings to have the engine run nice and smooth and regulate emissions.

Symptoms Of Code P0031

You may have a sense of the error code ahead of the appearance from the following symptoms. They include:

What Causes Code P0031?

Trouble code p0031 is a generic code, which means it can be triggered by more than one issue. Here are some of the causes;

  • Defective 02 sensor
  • Outdated software or failure in the onboard computer
  • Damaged oxygen sensor wires or poor connections
  • Blown P0031 fuse
  • Faulty heater circuit or connectors

How Serious Is Code P0031?

Code P0031 may cause your vehicle to run rough; it’ll not stop it from running though. The most common symptoms and effects are low fuel economy and rough engine operation.

In any case, if you fail to track down and fix the culprit, it may result in rough idling and cause severe damage to system components.

Common P0031 Diagnosis Mistakes

You must avoid some diagnosis mistakes that can aggravate the problem further. Here you go:

  • Replacing H02S before inspecting the connectors and wiring.
  • Make sure the ground wire is good and the sensor has up to 12 volts
  • Not properly checking both wirings and connectors to ensure they are in good condition.

Tools Needed To Diagnose Code P0031

Two urgent tools for smart and efficient diagnosis of code P0031 are:

  • Multimeter
  • OBDII Scan Tool

Code P0031 Diagnose And Repair

Once you make a successful diagnosis of the error, you must act sooner to get rid of the hassle. Not to downplay, the P0031 error code is not that grievous a problem to cause an immediate halt on the move but idling time away will amount to worsening consequences. Below you go with the expert advice to act the moment you spot the error code.

  • Scan the vehicle with your OBDII scanner and see if there’s any trouble code that is logged along with the P0031 fault code
  • Visually inspect bank 1 oxygen sensor one wiring and connection for disconnection, blowing, and fraying.
  • Check the heater element ground continuity.
  • It should have a good continuity; repair wiring it doesn’t.
  • Turn off the engine and leave the key in the ON position and check the battery voltage. It should be approximately 12 volts. The volt on the oxygen sensor heater should be the same as the battery volt.
  • If there’s no voltage on the 02 sensor heater, remove and inspect the fuse. If the fuse is working fine, you may have open/short heater circuit wiring. Consider repairing it.
  • If the voltmeter records less than 12 volts, check the wiring and connector for high resistance.
  • If you get 12 volts readings, you have a faulty oxygen sensor in place that needs replacement.

p0031 toyota location

Estimated Cost of Fixing

Vehicle Name Problems with p0031 Code Estimated Cost of Parts and Labor Estimated Total Cost
Toyota Bank 1 02 sensor 1 $50-100 + $50 $100-150
Ford Bank 1 02 sensor 1 $70-120 + $50 $120-170
Honda Bank 1 02 Sensor 1 $40-100 + $50 $90-150
BMW Bank 1 02 Sensor 1 $70-150 + $50 $120-200
VW Bank 1 02 sensor 1 $30-90 +$50 $80-140
Audi Bank 1 02 sensor 1 $50-100 +$50 $100-150
Nissan Bank 1 02 Sensor 1 $40-70 + $50 $90-120
Suzuki Bank 1 02 Sensor 1 $50-100 + $50 $100-150
Subaru Bank 1 02 senor 1 $50-100 + $50 $100-150
Dodge Bank 1 02 sensor 1 $60-120 – $50 $110-170
Jeep Bank 1 02 sensor 1 $40-100 + $50 $90-150

The price above is just a rough estimate. The price can be above or less than the price, but it’ll fall within that range. Again, the problems could be wiring or connector issues and not the sensor itself.

Same Problems With Different Error Codes

To complete the course, you must know what other error codes may prompt the same issues as caused by P0031 code. And no need to tell that they too require the same fixes.

  • P2195
  • P0052
  • P0032
  • P0030
  • P0135 Ford


Q: Can I drive with P0031?

Code P0031 will not keep you stranded on the road but do not allow the issues to linger because it can result in poor engine operation, high fuel consumption, sensor loop failure, and the issue can extend to other system components.

Q: Is the P0031 code bad?

Code P0031 is not bad as it can not stop a car from running. The most common effect is bad fuel mileage and erratic idling. However, it can cause severe damages to related components if it stays unresolved for an extended period.

Q: What is H02S?

H02 means several things; it can be referred to as water in chemistry. But in the automotive industry, H02S stands for Heater control circuit sensor. It also stands for heated oxygen sensor.

Q: What is H02S heater control circuit low?

Heater control circuit low refers to a lousy or malfunctioning in the heater circuit of an 02 sensor. The heating circuit, otherwise known as the heater element, is an essential part of the oxygen sensor that heats the sensor to normal operating temp until the engine gets hot.

Q: Is bank 1 sensor 1 left or right?

There are several auto manufacturers with different ways of designing their engines. What do I mean? In some cars, bank 1 can be on the right engine side, while other engines have bank 1 on the right side.

Bank 1 sensor 1 is typically located in the side of the engine that has the no.1 cylinder. However, on every bank, there are two oxygen sensors attached to it, which makes it four sensors in total.

Let’s assume your no.1 engine is located on the left side of the engine. That said, the 02 sensor located upstream of the exhaust [before the catalytic converter] is the bank 1 sensor 1. Bank 1 sensor 2 is the next sensor located downstream [after the catalytic converter]. The same applies to bank 2 sensors.

Final word

Timely engine tune-up and maintenance will enhance the engine performance and help the car run smoothly without the P0031 code logging on.

Indeed, P0031 can cause several system malfunctions, but regularly scheduled maintenance can minimize the system component damages.

Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

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