Air & Fuel Mixture ControlOBD2 Codes

P0031 – Meaning, Causes, Symptoms, & Fixes

Code P0031 Definition

HO2S Heater Control Circuit Low (Bank 1, Sensor 1)

What Does P0031 Mean?

The P0031 code is a result of the bank 1 HO2S1 (pre catalytic converter heated oxygen sensor) heating element having low voltage. Heated O2 sensors have a seperate heater inside the sensor to get them to operating temperature quickly. The faster your O2 sensor(s) get to operating temperature, the faster the car is in a fuel efficient and emissions friendly configuration. If this code is set, the oxygen sensor heater is not working.

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What Are the Symptoms of Code P0031?

*No noticeable adverse conditions in some cases

What Is the Cause of Code P0031?

  • Frayed heater circuit wiring/connectors
  • Faulty heater circuit fuse
  • Faulty heated oxygen sensor
  • Malfunctioning PCM/ECM

How Serious Is Code P0031? – Moderate

This trouble code will not prevent your vehicle from running. The most common result(s) are lower fuel economy and poor vehicle operation. However, if left unsolved, this code could increase the likelihood of your vehicle running rough and cause potential damage to other components of your vehicle.

Code P0031 Common Diagnosis Mistakes

Prematurely replacing the heated oxygen sensor before attempting to visually inspect the wiring around the oxygen sensor for chafed/frayed wiring.

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Tools Needed to Diagnose Code P0031:

How to Diagnose and Repair Code P0031:

Difficulty of Diagnosis and Repair – (3 out of 5)

  1. Check to see if there are any other codes along with P0031 and clear your Check Engine Light with FIXD.
  2. Conduct a visual inspection of bank 1 pre catalytic converter oxygen sensor wiring for fraying and/or disconnection.
  3. Check the ground side of the O2 sensor’s heater circuit for continuity to ground. It should have good continuity if it doesn’t, repair wiring.
  4. With the engine off and the key “on”, use a voltmeter to check for approximately 12 volts (should be the same voltage the vehicle battery is at) on the power side of the O2 sensor heater. 
    1. If no voltage is registered, check the fuse; if the fuse is good, consider repairing short/open in heater circuit wiring.
    2. If low voltage is measured, check for high resistance in the wiring.
    3. If the voltmeter registers 12 volts, consider replacing the heated oxygen sensor.

Estimated Cost of Repair

For error code P0031, one or more of the below repairs may be needed to solve the underlying issue. For each possible repair, the estimated cost of repair includes the cost of the relevant parts and the cost of labor required to make the repair. 

  • Oxygen sensor $200-$300
  • Wiring repair/replacement $100-$1000

Lifelong automotive enthusiast with a soft spot for offroading. Wrencher turned writer, but I still love to tinker on just about anything with an engine. Dream car: tie between a ‘71 Hemi ‘Cuda and a ’91 GMC Syclone. #GirlDad #SaveTheManuals

Jeffrey N. Ross
Lifelong automotive enthusiast with a soft spot for offroading. Wrencher turned writer, but I still love to tinker on just about anything with an engine. Dream car: tie between a ‘71 Hemi ‘Cuda and a '91 GMC Syclone. #GirlDad #SaveTheManuals

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  1. Here is your FIXD REPORT CODE

  2. I think this is a factor but not sure if this is exactly the problem. I change the motor in this Ion. And man it fired right if it just run out of gas.. And I was happy to know I got a good motor but then I had starter problems. And I replaced it and I wired it up but I had the ground wire on where it should have been the alternator.. But it didn’t take long cause it just was clicking when I truned the key as before it was starting up no problem.. But then it happened. Went to start it and it was nothing just the ring of the ignition and door bells… Lol. No start no nothing.. What would you think happened.. Is the security styem locked.?
    Cause I had it turn over a couple times and it sounded like no fuel is getting their and no fire.. And the security lights is coming on but it goes off It’s a yellow sign with a lock and a car . And it’s sales locked.. Pls help if you can. Don’t know what else to do. Thanks.

  3. So it needs new O2 sensors?

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