Air & Fuel Mixture ControlOBD2 Codes

P0131 – Meaning, Causes, Symptoms, & Fixes


What Does Code P0131 Mean?

  • P0131 definition: O2 Sensor Circuit Low Voltage (Bank 1, Sensor 1)
  • Issue Severity: MODERATE – Extended driving with this code may cause internal engine damage.
  • Repair Urgency: Get this code fixed as soon as possible to avoid emission system and catalytic converter damage.
  • Diagnosis: Driving with trouble code P0131 is acceptable but only for a short period of time. Driving with this code for an elongated period of time could result in greater engine damage if it is being caused by a lean air/fuel ratio.

Code P0131 is a result of the oxygen sensor incorrectly detecting the air/fuel ratio of the exhaust. This ratio is sent to the ECM which uses this data, along with comparisons to the outside air, to regulate the air to fuel ratio needed by the engine. This code is the result of this ECM detecting either a voltage outside of the specified range or an improper air to fuel ratio.

P0131 Causes

There are many potential causes of code P0131.

  • Faulty oxygen sensor (most common)
  • Short on voltage to O2 circuit
  • Exhaust leaks
  • Fuel pressure low
  • Engine running lean

P0131 Symptoms

  • Check Engine Light
  • Possible exhaust leaks
  • Exhaust odor
  • Vehicle running rough
  • Lack of power
  • No adverse conditions in some cases

How Do I Fix Code P0131?

With an oxygen sensor fault, the first step is to get it diagnosed to figure out what is causing the problem. 

If your vehicle has this fault and you’re not comfortable diagnosing this issue at home, we recommend finding a RepairPal certified shop nearby to pinpoint the problem and give an accurate estimate for repairs. 

These shops can not only help you figure out what’s going wrong before you waste time and money on the wrong parts, but they also offer a minimum 12-month, 12,000-mile warranty and stand behind all their estimates with guaranteed fair pricing.

> Find a RepairPal Certified Shop Near You

How Much Does It Cost to Fix Code P0131?

P0131 can be caused by anything from a failed O2 sensor to faulty wiring to leaks in the exhaust. It’s impossible to give an accurate estimate without properly diagnosing the issue first. 

If you take your car to a shop for diagnosis, most shops will start with an hour of “diag time” (the time spent in labor diagnosing your specific issue). Depending on the shop’s labor rate, this typically costs somewhere between $75-$150. Many, if not most, shops will apply this diagnosis fee to any required repairs if you have them perform the repairs for you. From there, a shop will be able to give you an accurate estimate for repairs to fix your P0131 code.

Possible Repair Costs for P0131

For error code P0131, 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
  • Exhaust repair $100-$200 (if welded to repair)
  • Fuel Pump $1300-$1700
  • Fuel pressure regulator $200-$400
  • Vacuum leak $100-$200

DIY Steps to Diagnose Code P0131

Engine code P0131 could be caused by a number of things, including a bad oxygen sensor, faulty wiring, or an exhaust leak. If you’d like to try to fix code P0131 at home without throwing money at parts, you’ll want to follow the steps below for proper diagnosis. Keep in mind this is an intermediate-level diagnosis and repair and not recommended for beginners. Diagnosis requires more specialized equipment beyond what the FIXD Sensor can provide and it can be a time and labor-intensive process for inexperienced DIYers.

DIY difficulty level: Intermediate

This repair requires mechanical knowledge and is not recommended for beginners.

Tools/parts needed (our top picks from Amazon):


Visually inspect the O2 sensor wiring and harness connections for any corrosion in the connections or for any physical damage that might be present. Repair as needed.


Look for any exhaust leaks between the engine and the O2 sensor. That includes the exhaust manifold or headers, the area around the turbocharger if your vehicle has one, flex pipes, and the catalytic converter(s). Repair as needed.


Warm up your engine. Using FIXD Live Data, look at your O2 sensor (bank 1, sensor 1) voltage. Check your vehicle service manual to determine what the proper voltage range is for this sensor. If the voltage you see is outside this range, you most likely have a faulty O2 sensor. To be sure, continue diagnosis.


Using a fuel pressure gauge, check the fuel pressure and compare it to your vehicle specification. Too low fuel pressure can cause the engine to run lean, causing the O2 sensor to read low voltage as described in step 3. In this case, the sensor is accurate, and the lean running condition needs to be fixed.


Conduct a visual and audible inspection of the vacuum lines and any intake connections to make sure there are no signs of disconnection or outside air leaks. This includes the intake pipe between the throttle body and mass air flow sensor. Listen for a hissing sound coming from these lines, which can be a sign of a vacuum leak. Spray water over intake area and listen. If the engine briefly stumbles and runs rough, then recovers, there is most likely an intake leak. Concentrate the water stream on different hoses and gaskets until you find your leak.

Common P0131 diagnosis mistakes

Replacing the O2 sensor without checking for any exhaust leaks or loose connections.

Still Need Help Fixing Code P0131?

If you’ve followed the steps above and are still experiencing check engine code P0131, please contact the FIXD Mechanic Hotline if you’re a FIXD Premium subscriber or find a RepairPal certified shop near you to get the right repairs at a fair price.


Recovering autocross and track day enthusiast. Once turned a VW Jetta into a pickup truck. Lives in a van down by the river. Dream car: 2001 Subaru WRC rally car.

Justin Hughes
Recovering autocross and track day enthusiast. Once turned a VW Jetta into a pickup truck. Lives in a van down by the river. Dream car: 2001 Subaru WRC rally car.

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    1. Cleared code and light did not come on again car is running fine

    2. The battery of the car was dead. I jump the car and as soon it turn on, the check engine light came on and this code appears. After a couple of hours, running around, erased the code, all back to normal. I tested the car days after and check light do not come back again. Your tool and service is awesome!!!

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    4. Could this code also be caused by driving to an higher elevation. Let’s say 2000-3000 feet above normal daily driving?

    5. FIXD diagnosed my check engine light correctly. Once I cleared the light I took the truck for a drive and did not notice any performance issues. Thanks for solving a potential problem. FIXD is the best purchase I ever made.

      1. My car all the sudden started putting and died, we got stranded with our 3month old baby and had to pat for a tow! I hope this dont cost me another arm and a leg! Fix showed 5 codes ?

    6. When I go to the shop I tell my mechanic what my car needs

    7. So my car is showing code 131 means my 02 sensor need changing …

    8. Could this code have anything to do with the fact I cut off the muffler

    9. My car all the sudden started putting and died, we got stranded with our 3month old baby and had to pay for a tow! I hope this dont cost me another arm and a leg! Fix showed 5 codes ?

    10. I changed both of my 02 sensor on my 02 Honda Civic and my engine light still stay on and am still getting the p0131 code what am I missing please help

      1. Did you disconnect the battery and reconnect it again after you changed your O2 sensors? If yes then you might need to replace your catalytic converter.

    11. My 2018 Buick Encore had a code of p301 which is misfire moved spark plug of number 1to 4 and the turned car back in to read a code now shows new code of p131 any idea why or how this could happen esp when goes from one code to another? Running very poor feels like going stall out. Any ideas?? Please help!!

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