What does this cost in your state?
California is the costliest state and Arkansas the cheapest; each square shows that state's midpoint of the estimate.
Lower-cost states ($375)MiddleHigher-cost states ($478)
What it shows: CA is the highest at $478 and AR the lowest at $375, across 51 states.
Counts below are complaints filed with NHTSA, not failure rates: a longer bar means more owners reported it.
Is your car affected?
What it shows: The most common band for complaints about this repair is 50,000-100,000 (34%). The biggest difference from all complaints is under 50,000: 31% against 60%.
What it shows: The most common band for complaints about this repair is 6-9 years (45%). The biggest difference from all complaints is under 3 years old: 16% against 40%.
Is it urgent, and what do owners notice first?
281 owner complaints name this part.
What owners describe. Warning light: 57%; Stalled or lost power: 25%; Dealer could not fix or repeat repair: 23%.
Owners say the dealer could not fix or repeat the problem. If it comes back after a repair, ask what was tested before you pay again.
Which trouble codes do owners report?
P0420 Catalyst System Efficiency Below Threshold leads at 7.
Trouble codes owners quote in complaints about this part. P0420: Catalyst System Efficiency Below Threshold: 7 complaints (2%).
Which other parts do owners name in the same complaint?
Among the 281 owner complaints naming this part, catalytic converter is named in 29% of them, more than any other part.
Other parts named in the same complaints. Catalytic converter: 29%; Spark plug: 13%.
Owners name the catalytic converter most often in the same complaint, which is not proof that one caused the other. Ask the shop whether it checked the catalytic converter too, so you are not quoted twice for one visit.
How fast were owners driving when it happened?
55 mph or faster leads at 41%.
Owners reported it most often at highway speed. Tell the shop what speed it happens at, because that narrows the diagnosis.
How serious did it get for owners?
Among the 281 owner complaints naming this part, being towed is the outcome owners report most often.
Outcomes owners reported in complaints about this part. Towed: 17; Fire reported: 4; Crash reported: 2.
Which model years show up most in the complaints?
Among the 281 owner complaints naming this part that state a model year, complaints cluster in a few model years instead of spreading evenly.
What it shows: 2015 is the largest at 65 (23%), followed by 2016 at 59 (21%); the smallest shown is 2025 at 2 (1%).
Is this repair covered by an emissions warranty?
Federal rules require carmakers to cover the catalytic converter, the emissions computer and the onboard diagnostic system for 8 years or 80,000 miles, and any part whose failure fails an emissions test for 2 years or 24,000 miles; California requires 3 years or 50,000 miles on every emission part.
| Warranty | Covers | Length |
|---|---|---|
| California, all emission parts | All emissions-related parts | 3 years or 50,000 miles |
| California, high-cost parts | Specific high-cost emission parts listed in the owner manual | 7 years or 70,000 miles |
| Federal, basic | Any part that causes an emissions failure | 2 years or 24,000 miles |
| Federal, extended | Catalytic converters, electronic emissions control unit (ECU), onboard emissions diagnostic device or computer (OBD) | 8 years or 80,000 miles |
What do emissions repairs cost?
Among 46,033 California vehicles repaired to pass a Smog Check in 2025, 39.1% cost over $650 to fix and the average bill was $757.
What it shows: Over $650 is the largest at 39.1%, followed by $1 to $100 at 13.1%; the smallest shown is $501 to $650 at 8.4%.
Do ignition and engine sensors problems track on-road nitrogen oxide emissions, tons per year per 1,000 residents across states?
Across U.S. states, NHTSA owner complaints about ignition and engine sensors problems run higher where on-road nitrogen oxide emissions, tons per year per 1,000 residents is higher, after adjusting for the makes sold in each state. This is an association across states, not proof that on-road nitrogen oxide emissions, tons per year per 1,000 residents causes this repair. Too few complaints name this repair alone, so the on-road nitrogen oxide emissions, tons per year per 1,000 residents pattern is measured across all 19,176 complaints about the ignition and engine sensors, which this repair belongs to.
How to read it: Each dot is a state. Further right means more on-road nitrogen oxide emissions, tons per year per 1,000 residents (epa nei 2020); higher up means more complaints for this repair than expected (1.0 is average). If the dots climb to the right, reports of this repair rise with on-road nitrogen oxide emissions, tons per year per 1,000 residents (epa nei 2020).
What it shows: States with more on-road nitrogen oxide emissions, tons per year per 1,000 residents (epa nei 2020) tend to sit higher on the chart across 50 states: a pattern in the data, not proof of cause.
- The 10 states with the most on-road nitrogen oxide emissions, tons per year per 1,000 residents (Wyoming, Montana, New Mexico, North Dakota, Idaho, South Dakota, Nebraska, Oklahoma, Oregon, Kansas): reports of ignition and engine sensors problems run 2% above what the makes sold there would predict, and 6 of 10 are above expected. The 10 with the least (District of Columbia, New York, Massachusetts, New Jersey, Vermont, California, Hawaii, Rhode Island, Maryland, Michigan): 3% below, and 3 of 10 are above expected.
- Exceptions: Montana, New Mexico and Idaho are among the highest in on-road nitrogen oxide emissions, tons per year per 1,000 residents but report below expected.
- Split the states into thirds: the third with the least on-road nitrogen oxide emissions, tons per year per 1,000 residents runs 4% below what the makes sold there would predict, the middle third 4% above, and the third with the most 6% above. Most of the on-road nitrogen oxide emissions, tons per year per 1,000 residents effect sits between the lowest and the middle third.
- For on-road nitrogen oxide emissions, tons per year per 1,000 residents, after allowing for the 1562 comparisons we ran, luck alone would produce a pattern this strong about 1 time in 8. The on-road nitrogen oxide emissions, tons per year per 1,000 residents pattern leans on District of Columbia: without it, it weakens.
- Weak spot: compare only states with similar cost of living index and the pattern keeps about 24% of its strength, so part of it may come from cost of living index instead of on-road nitrogen oxide emissions, tons per year per 1,000 residents.
- For on-road nitrogen oxide emissions, tons per year per 1,000 residents, of the 5 exception states, 4 read the same way for the other parts of the ignition and engine sensors (so that is the system there, not this repair) and 1 are specific to this repair.
Where the on-road fleet puts out more nitrogen oxide per resident, emission-control parts are working harder and the places are more likely to enforce emission rules.
Do ignition and engine sensors problems track gallons of motor gasoline burned per resident per year across states?
Across U.S. states, NHTSA owner complaints about ignition and engine sensors problems run higher where gallons of motor gasoline burned per resident per year is higher, after adjusting for the makes sold in each state. This is an association across states, not proof that gallons of motor gasoline burned per resident per year causes this repair. Too few complaints name this repair alone, so the gallons of motor gasoline burned per resident per year pattern is measured across all 19,176 complaints about the ignition and engine sensors, which this repair belongs to.
How to read it: Each dot is a state. Further right means more gallons of motor gasoline burned per resident per year (seds, transportation); higher up means more complaints for this repair than expected (1.0 is average). If the dots climb to the right, reports of this repair rise with gallons of motor gasoline burned per resident per year (seds, transportation).
What it shows: States with more gallons of motor gasoline burned per resident per year (seds, transportation) tend to sit higher on the chart across 50 states: a pattern in the data, not proof of cause.
- The 10 states with the most gallons of motor gasoline burned per resident per year (Alabama, Wyoming, Mississippi, South Carolina, North Dakota, Missouri, South Dakota, New Hampshire, Arkansas, Kentucky): reports of ignition and engine sensors problems run 6% above what the makes sold there would predict, and 8 of 10 are above expected. The 10 with the least (District of Columbia, New York, Hawaii, California, Washington, Illinois, Oregon, Rhode Island, Pennsylvania, Alaska): 0% below, and 5 of 10 are above expected.
- Exceptions: Mississippi and South Carolina are among the highest in gallons of motor gasoline burned per resident per year but report below expected.
- Split the states into thirds: the third with the least gallons of motor gasoline burned per resident per year runs 1% below what the makes sold there would predict, the middle third 1% below, and the third with the most 4% above. Most of the gallons of motor gasoline burned per resident per year effect sits in the third with the most.
- For gallons of motor gasoline burned per resident per year, after allowing for the 1562 comparisons we ran, luck alone would produce a pattern this strong about 1 time in 7. The gallons of motor gasoline burned per resident per year pattern leans on District of Columbia: without it, it weakens.
- Weak spot: compare only states with similar cost of living index and the pattern keeps about 24% of its strength, so part of it may come from cost of living index instead of gallons of motor gasoline burned per resident per year.
- For gallons of motor gasoline burned per resident per year, of the 5 exception states, 4 read the same way for the other parts of the ignition and engine sensors (so that is the system there, not this repair) and 1 are specific to this repair.
Where residents burn more gasoline they drive more miles, and brakes, tires, belts and suspension wear out with miles.
Are the parts for this repair getting more expensive, or only the labor?
The federal producer price index for new electrical and electronic engine equipment parts rose 57.0% from December 2019 to August 2026, while the consumer price index for motor vehicle repair, labor and parts together, rose 55.2% (BLS, national).
Prices of new electrical and electronic engine equipment parts, as shops buy them from makers, since December 2019, against consumer prices for motor vehicle repair. New electrical and electronic engine equipment parts: +57.0%; All motor vehicle parts: +17.4%; Motor vehicle repair, labor and parts together: +55.2%.
If my car fails smog, how much of this repair must I pay, and does California help?
California caps required Smog Check repair spending at $650 through a repair cost waiver and its Consumer Assistance Program pays up to $1,450 of repairs for qualifying owners of 1996 and newer cars, so on a typical $432 oxygen sensor replacement the program would pay $346 and the owner $86.
| Rule | Amount | What it means at $432 |
|---|---|---|
| CAP repair assistance, model year 1976 to 1995 | up to $1,100 | you pay 20% up to $1,375 of repairs, then everything above $1,100 |
| CAP repair assistance, model year 1996 or newer | up to $1,450 | On a oxygen sensor replacement at $432 the program pays $346 and you pay $86 |
| CAP vehicle retirement | up to $2,000 | paid instead of repair when you retire the car |
| Repair cost waiver line (every Smog Check failure) | $650 | A oxygen sensor replacement at $432 is under the line, so no waiver |
| Roadside re-failure within a year, model years 2000 to 2006 | 17% after passing, 35% after failing first | 7,886 cars checked in CY 2017-2018 |
After a failed emissions test, who can repair it, and what do repairs cost?
Maryland lists 135 certified emissions repair facilities and New Jersey 332, while Texas inspectors logged about 21,000 emissions repairs costing $3.7 million across its two inspection areas in 2024 and 2025, with a median repair cost of $25 to $299 by category after dropping zero and over-$2,000 entries.
| Program | What the public record shows | Count or figure |
|---|---|---|
| Maryland certified emissions repair facilities | 13 counties; most in Baltimore 31, Montgomery 24, Anne Arundel 17 | 135 facilities |
| New Jersey emission repair facilities | 218 also run private inspections | 332 facilities |
| Texas program evaluation, repair records | repairs logged by inspectors, Dallas-Fort Worth and Houston areas, 2024 and 2025 | about 21,000 repairs, $3.7 million |
| Texas repair cost per repair (median and mean ranges) | by repair category, after dropping zero entries and costs above $2,000 | median $25 to $299, mean $82 to $415 |
| Texas repair records logged at zero cost | inspectors enter the cost by hand; the report warns of entry errors | 68.1% of records |
Has this part been recalled abroad on cars that may share it?
Manufacturers filed 2 foreign recall campaigns that name oxygen sensor with NHTSA since 2015 (matched by the filing text); the latest, from Chrysler (FCA US in 2025-10.
| Filed | Manufacturer | Foreign recall no. | What the filing says |
|---|---|---|---|
| 2025-10 | Chrysler (FCA US) | 158 | Date of Report: 10/01/2025 Determined by: Manufacturer's Name - Brand Name FCA Brazil - Jeep Report Type Quality Field Action Identification of Affected Vehicles: Model Year(s) Inclusive Dates of Affected Start End Manufacture Model Population Make(s) Model(s). |
| 2018-08 | Suzuki Motor | 147 | Description of Condition An error in the diagnostic system program can allow incorrect identification of a faulty oxygen sensor under certain operating conditions. |
Does my county fall under federal smog rules or breathe unhealthy air?
EPA's Green Book lists 203 counties as currently nonattainment for ozone or fine particles, home to 39.6% of U.S. residents; the shares run highest in DC, NJ and CA (100.0%, 100.0%, 94.9%).
| State | Share of residents | Nonattainment counties |
|---|---|---|
| DC | 100.0% | 1 |
| NJ | 100.0% | 21 |
| CA | 94.9% | 38 |
| MD | 88.4% | 12 |
| DE | 81.6% | 2 |
| UT | 79.4% | 7 |
| NV | 73.0% | 1 |
| IL | 71.7% | 11 |
| AZ | 68.5% | 3 |
| CO | 68.0% | 9 |
| Median state | 0.0% |
Which emission standard was my car certified to?
EPA's certification records show 100.0% of model year 2014 light-duty carlines certified to the older Tier 2 exhaust standard and 79.1% of model year 2026 carlines certified to Tier 3 Bin 50 or cleaner, so the catalytic converter and sensors a car needs depend on its model year (one count per carline, not per car sold).
| Model year | Tier 2 (older standard) | Tier 3 Bin 70 to 160 | Tier 3 Bin 20 to 50 (cleaner) | Tier 3 Bin 0 (zero emission) |
|---|---|---|---|---|
| 2014 | 100.0% | 0.0% | 0.0% | 0.0% |
| 2016 | 95.6% | 3.1% | 1.2% | 0.1% |
| 2018 | 3.1% | 82.4% | 12.8% | 1.8% |
| 2020 | 2.4% | 69.8% | 24.7% | 3.1% |
| 2022 | 0.2% | 53.2% | 38.3% | 8.3% |
| 2024 | 0.3% | 34.5% | 43.5% | 21.7% |
| 2026 | 0.1% | 20.7% | 48.1% | 31.0% |
How often does this part fail a real inspection, by car age?
In 2,102,125 New Jersey initial inspections in 2025, 14.3% of cars aged 16+ years failed the emissions test against 2.8% of cars under 3 years, about 5 times as often (record counts, not a sample).
What it shows: 16+ is the largest at 14.3%, followed by <3 at 2.8%; the smallest shown is 3-4 at 2.6%.
Has the maker published a fix?
A bulletin is a repair procedure a maker sends its dealers, not a safety defect: if your maker is listed, ask the dealer whether one covers your car and quote its number.
| Maker | Vehicles | Bulletin number | Date | What it says |
|---|---|---|---|---|
| Subaru | Outback 2020–2024; Crosstrek 2017–2024 and 4 more | 09-115-24R | Sep 3, 2024 | This bulletin announces the availability of new oxygen sensors developed to address Diagnostic Trouble Codes (DTCs) detected by the Engine Control Module. |
| Subaru | Impreza 2017–2024; Outback 2020–2024 and 4 more | 09-115-24 | May 14, 2024 | This bulletin announces the availability of new oxygen sensors developed to address the following Diagnostic Trouble Codes (DTCs); P0137 (O2 Sensor Circuit Low Voltage Bank 1 Sensor 2, P0138 (O2 Sensor Circuit High Voltage Bank 1 Sensor 2) P0140 (O2 Sensor. |
| Porsche | Cayenne S 2020 | 2009.3 | Jan 4, 2024 | Instructions on advanced technical information for the downstream oxygen sensor. |
| Porsche | Panamera 4 E-Hybrid 2017–2023 | 96-23-1 | Aug 7, 2023 | Technical information on a message that states "engine control fault" in the instrument cluster/fault memory entries for the oxygen sensor downstream of the catalytic converter. |
| Nissan | Sentra 2015–2016; Altima 2015–2016 | NTB22-007A | Mar 2, 2022 | 2013-2016 altima and sentra; rear oxygen sensor voltage inspection This bulletin has been amended. |
| Lexus | IS 500 2022; RC F 2022 | L-TT-0311-22 Rev | Feb 17, 2022 | TT: Customers may complain of a MIL ON condition. |
37 more bulletins name this part; the car finder at the top checks yours, and the NHTSA bulletin file linked below lists them all.
Manufacturer warranty extensions naming this part (4)
| Maker | Vehicles | Date | Notice number | What the maker extended |
|---|---|---|---|---|
| Nissan | Altima 2013–2016; Sentra 2013–2016 | Mar 15, 2022 | NTB22-007 | Rear oxygen sensor short-to-ground. |
| Nissan | Altima 2013–2016; Sentra 2013–2016 | Mar 15, 2022 | PC857_PM997 2013 | Rear oxygen sensor short-to-ground condition and masked diagnostic. |
| BMW | 750li 2009–2015 | Aug 31, 2020 | B010319 | Rear monitoring oxygen sensors defects in materials. |
| Audi | S6 2016–2018; S8 2016–2018 | May 7, 2020 | AWA 20 | Rear oxygen sensor. |
What do owners say?
2 complaints quoted word for word, each with its NHTSA number.
First, this is a brand new purchase and vehicle had less than 6K miles before electrical issues with oxygen sensors (3), which all had to be immediately replaced.
The rear O2 sensor failed on my 2017 Nissan Altimas with only 29,900 miles on it and it cost me almost $400.00 to replace it.This is a part that should easily last for 150,000 miles.
Check your car
Our calculator's default estimate is $296–$568 for one upstream (pre-cat) oxygen sensor at a chain shop. Three things move it: whether the sensor sits before or after the catalytic converter, how many sensors the shop replaces, and what kind of shop does the work.
What does the oxygen sensor estimate cover and leave out?
The estimate covers the sensor and the shop labor to swap it, for the sensor position, sensor count and shop type named beside the range. The default is a chain shop, which sits between an independent shop and a dealer. It is a range for a typical car, not a quote for yours.
It leaves out whatever a shop adds on top. Ask whether the quote includes a scan to confirm which sensor failed, since that diagnostic can be billed separately. Ask whether it includes a new gasket or thread treatment for a sensor that is stuck in the exhaust, and whether clearing the check engine light and a test drive are part of the price. Taxes and disposal fees are separate too.
If a quote lands well above the range for your sensor position, ask what is being added before you pay.
How much do sensor location, count and shop type change the price?
Here are the calculator's ranges for each setting. Every row keeps the other inputs at the default.
| Setting | Estimate |
|---|---|
| Default: one upstream sensor, chain shop | $296–$568 |
| One downstream (post-cat) sensor, chain shop | $204–$444 |
| Two upstream sensors, chain shop | $592–$1,136 |
| One upstream sensor, independent shop | $280–$540 |
The upstream sensor row sits above the downstream one in the calculator. Replacing two sensors doubles the figure, which is why the sensor count matters more than the shop. The independent shop row is only a little below the default, so choosing a shop type alone will not rescue an inflated quote.
The calculator cannot know which of your sensors is failing, so run the combination your shop names instead of adding rows in your head.
How do I know which sensor needs replacing?
A shop finds the failing sensor by reading the trouble code with a scan tool. The code tells the shop which position and which side of the engine to look at. Ask the shop to give you that code in writing, then ask which sensor it points to and why.
A code is a pointer, not a verdict, because the same code can come from a different fault. Ask whether the shop checked the sensor's wiring before replacing it, and whether it expects the code to return after the swap.
How do I get a fair quote?
Compare quotes against the calculator range for your sensor position and count, not against each other alone. A quote far below the range may leave something out, such as the diagnostic or the code clearing. A quote far above it deserves a question about what extra work is included.
Ask what warranty comes with the sensor and the labor, and whether it is in writing. If the check engine light returns soon after the swap, a shop that stands behind the work will look again at no charge.
Frequently asked questions
Can I replace an oxygen sensor myself?
Some owners do when the sensor is easy to reach. A stuck sensor in a hot exhaust can be hard to remove, and you still need to know which one failed. Check your service manual first.
Is an aftermarket sensor as good as the original?
Ask the shop which brand it uses and what warranty comes with it. A cheaper sensor with a short warranty can cost more if it fails again and the labor is billed twice.
Does an independent shop cost less than a dealership?
Usually the hourly rate is lower at an independent shop, but compare the written quotes, because the sensor price and the extras decide the total.
Sources
Data shown on this page
- NHTSA owner complaint file (2015-2019 · 2020-2024 · 2025-2026) file downloaded 2026-10-05
- NHTSA service bulletin file (2015-2019 · 2020-2024 · 2025-2026) file downloaded 2026-10-05
- CalcScrape calculator model scaled by BEA Regional Price Parities data from 2024
- U.S. Code of Federal Regulations, 40 CFR 85.2103, and the California Air Resources Board warranty fact sheet file downloaded 2026-10-05
- California Bureau of Automotive Repair, Smog Check Executive Summary Report 2025 data from 2025
- EPA 2020 National Emissions Inventory, on-road, joined to NHTSA owner complaints file downloaded 2026-10-06
- EIA State Energy Data System, motor gasoline consumption, joined to NHTSA owner complaints file downloaded 2026-10-06
- BLS Producer Price Index, commodity data for motor vehicle parts (series WPU1412051424); BLS Consumer Price Index item SETD for the repair row file downloaded August 2026
- California Bureau of Automotive Repair: Smog Check Reference Guide, Consumer Assistance Program repair assistance page, and 2019 Smog Check Performance Report data from 2025
- Maryland Department of the Environment (opendata.maryland.gov 7gas-4kz4), State of New Jersey open data (9qpt-bnm4), Texas Commission on Environmental Quality, Evaluation of the Texas Vehicle Emissions Inspection and Maintenance Program (2026) data from 2026
- NHTSA Office of Defects Investigation, Foreign Campaigns (filings under 49 CFR 579.11, public API) file downloaded 2026-10-05
- EPA Green Book, Currently and previously designated nonattainment areas by county; county population from the 2020 Census file downloaded 2026-09 (EPA export 2026-09-30)
- U.S. EPA, Annual Certification Data for Vehicles, light-duty vehicle models 2014-present (exhaust standard of every certified carline) file downloaded 2026-10
- New Jersey Motor Vehicle Commission, Vehicle Inspection Data file downloaded 2026-10
Terms: US government data, public domain.
Observed: records as filed; owner reports are unverified and are not failure rates. Modeled: our estimate, not a quote. Rule: a published legal rule, not a measurement; whether it covers a given repair depends on the car and the facts. Derived: computed from the records; an association, not a cause.
What is our own estimate
The price range comes from our calculator's formula. Its parts prices, labor hours per job and shop-rate tiers are CalcScrape estimates, not a published price dataset. Checked against RepairPal's range ($440–$523) on 2026-10-04: our default's midpoint is 10% below the middle of that range. Methodology