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 ($139)MiddleHigher-cost states ($177)
What it shows: CA is the highest at $177 and AR the lowest at $139, 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 3-5 years (37%). The biggest difference from all complaints is under 3 years old: 26% against 40%.
Which trouble codes do owners report?
P0302 Cylinder 2 Misfire Detected leads at 85.
The code owners quote most is P0302. Read your own code from a scan and give the shop the exact code, not only "the light is on".
What do owners say it led to?
Among the 13,993 owner complaints naming this part, owners most often say loss of power followed.
If your car shows the signs above, get it checked before it gets as far as loss of power.
Which other parts do owners name in the same complaint?
Among the 13,993 owner complaints naming this part, spark plug is named in 5% of them, more than any other part.
Other parts named in the same complaints. Spark plug: 5%; Engine overhaul: 3%.
Owners name the spark plug most often in the same complaint, which is not proof that one caused the other. Ask the shop whether it checked the spark plug too, so you are not quoted twice for one visit.
What did owners say they paid?
Half of the 56 owners who wrote a dollar amount gave $1,000 or less; one in ten wrote more than $10,000.
These are bills owners wrote down, often covering more than this one repair. They show how far a job can run; get written quotes for your own car.
How fast were owners driving when it happened?
55 mph or faster leads at 44%.
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 13,993 owner complaints naming this part, fire is the outcome owners report most often.
What it shows: Fire reported is the largest at 169, followed by Towed at 140; the smallest shown is Death reported at 2.
Which model years show up most in the complaints?
Among the 13,993 owner complaints naming this part that state a model year, complaints cluster in a few model years instead of spreading evenly.
What it shows: 2017 is the largest at 2,476 (18%), followed by 2015 at 1,785 (13%); the smallest shown is 2025 at 256 (2%).
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%.
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 $160 check engine light repair the program would pay $128 and the owner $32.
| Rule | Amount | What it means at $160 |
|---|---|---|
| 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 check engine light repair at $160 the program pays $128 and you pay $32 |
| 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 check engine light repair at $160 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 |
Who diagnoses this, and is there a shortage of them?
The Bureau of Labor Statistics counted 825,800 automotive service technicians in 2025, paid a median $50,620 a year, and projects 5% growth (40,900 jobs) to 2035; O*NET places the job in Job Zone Three: Medium Preparation Needed.
| Measure | Value |
|---|---|
| Jobs, 2025 | 825,800 |
| Median pay, 2025 | $50,620 a year ($24.34 an hour) |
| O*NET preparation level | Job Zone Three: Medium Preparation Needed |
| On-the-job training | Short-term on-the-job training |
| Projected growth, 2025 to 2035 | 5% (40,900 more jobs) |
| Typical entry-level education | Postsecondary nondegree award |
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 |
|---|---|---|---|---|
| Mazda | CX-50 2023–2025; CX-5 2023–2025 and 2 more | SA-048-26 | Aug 6, 2026 | Some vehicle may exhibit the CHECK ENGINE light on with DTC P0524 (Engine oil pressure control system: Oil pressure decrease) and no abnormal engine noise. |
| Mercedes-Benz | AMG GT63 4matic+ 2025–2026; AMG GT63 PRO 4matic+ 2025–2026 and 45 more | LI20.10-P-072886 | Jul 24, 2026 | Complaint Check Engine Light ON with DTC P012800 "The Coolant Temperature is Below the Specified Temperature" active and/or stored in the ME (N3/10). |
| RAM | 1500 2020–2023 | S2609000009 | Jun 15, 2026 | Check engine light (cel) illuminated with diagnostic trouble code (dtc) P0106 manifold absolute pressure sensor performance setting in the powertrain control module. |
| Mercedes-Benz | S 580 E 4matic 2023–2026 | LI07.70-P-080607 | Jun 3, 2026 | Complaint Check engine light activated. |
| Mercedes-Benz | Sprinter 1500 2023–2025; Sprinter 3500 2023–2025 and 1 more | LI09.41-N-080666 | Jun 3, 2026 | Check engine light with reduced power P300A6D due to charge air system contamination Complaint The check engine light is activated, accompanied by fault code 'P300A6D The boost pressure is too low', indicating reduced boost pressure. |
| RAM | 3500 2019–2025; 2500 2019–2025 | 9100692 Rev 1 | May 19, 2026 | On Cummins diesel applications that are for 2019 and newer the bpro part 1BP00507AB can on occasions create a check engine light. |
49 more bulletins name this part; the car finder at the top checks yours, and the NHTSA bulletin file linked below lists them all.
What do owners say?
4 complaints quoted word for word, each with its NHTSA number.
No check engine light or overheating, but this repair will cost was estimated as over $4k.
Didn’t even make it to 1000 miles check engine light came on, now being told it is the intake manifold that needs replaced not covered under warranty and this will cost me $1000 and still refuse to replace the problematic engine.
The problem was confirmed by check engine light and repaired by a Chrysler dealer for $3,500.
The check engine light came on and was locking itself in 4th gear and when returned to dealership they found it was the transmission shifter solenoid which was around a $700.00 to fix.
Check your car
Our calculator's default estimate is $120–$200. That is the diagnostic scan at an independent shop (about $100/hr) on a car 0–5 years old, with the scan fee included. The light itself is not the repair: the fix that follows decides the bill, and the calculator's repair rows run from $320–$565 up to $1,420–$2,845.
What does the check engine light price cover?
The default covers one thing: reading the car's computer and naming the fault code. It does not fix anything. If the shop already charged you for a scan, switch the calculator to "Already paid diagnostic" so the fee is not counted twice.
The repair rows cover the part and the labor for that one job at the same independent shop rate. They leave out taxes, a second fault the scan turns up, and any rusted or seized hardware that adds labor time.
How much does each common repair cost?
The calculator prices the four jobs that most often follow a scan. Age and shop type are shown in the same table.
| Setting | Estimate |
|---|---|
| Default: diagnostic scan, car 0–5 years old | $120–$200 |
| Diagnostic scan, car 6–10 years old | $132–$220 |
| Diagnostic scan, car 11–15 years old | $144–$240 |
| Diagnostic scan, car 15+ years old | $162–$270 |
| Oxygen sensor replacement | $390–$615 |
| Mass airflow sensor replacement | $350–$650 |
| Spark plugs or ignition coil | $320–$565 |
| Catalytic converter replacement | $1,420–$2,845 |
The repair rows assume an independent shop at about $100/hr. A chain or franchise shop is about $120/hr and a dealership about $175/hr in the calculator. The diagnostic scan is a flat fee, so those two shop types leave it at $120–$200. Only the hourly repairs get dearer there.
How do I tell what is wrong, and how urgent is it?
Schedule the scan soon when the light is steady. If it is flashing, stop driving and have the car checked before you go further.
The light alone cannot tell you the cause. Different faults trigger the same lamp, so the code from the scan is what decides the repair. Ask the shop to give you the code in writing, then compare it with the repairs in the table.
How do I get a fair quote?
Call two or three shops and give each the same details: year, make, model and the code from the scan. Ask what the diagnostic fee is and whether it is credited if you let that shop do the repair.
Ask each shop to separate the part, the labor hours and any fees. Then ask two questions that change the price. Is a cheaper part available that meets your car's specification? Has the fault been confirmed by a test, or is the shop replacing the likeliest part and hoping?
What does the estimate leave out?
The calculator gives a range for a typical car, not a quote for yours. Local shop rates differ from the figures here, and a second fault found during the scan is priced separately.
If a quote lands well above the range for the job named on your scan, ask what is being added before you pay. Enter your car in the calculator and take that range with you.
Frequently asked questions
Can I clear the light myself?
You can, but it will return if the fault is still there. Clearing it also erases the stored data a shop uses to find the cause.
Is the diagnostic fee refundable?
Some shops credit it toward the repair. Ask before you book, because policies differ by shop.
Should I drive with the light on?
A steady light can usually wait for an appointment. A flashing light means stop driving and have the car checked: tell the shop which one you have when you call.
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
- 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
- BLS Occupational Outlook Handbook, Automotive Service Technicians and Mechanics; O*NET OnLine 49-3023.00 file downloaded 2025 data, projections 2025 to 2035
- 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.
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 ($122–$233) on 2026-10-04: our default's midpoint is 10% below the middle of that range. Methodology