Emissions code
P0133: Oxygen sensor responding slowly (bank 1, before converter)
How this range is built
| Part of the job | Low | High |
|---|---|---|
| Parts | $40 | $180 |
| Labor: 0.6 to 1 hours × $125 to $175 an hour | $75 | $175 |
| Fees: shop supplies, disposal, diagnostics | $0 | $15 |
| Total, rounded | $110 | $370 |
The hourly rate is the BLS Occupational Employment and Wage Statistics, May 2025 average pay for this trade in Boston, $31.54 an hour, times 4 to 5.5 to cover what a shop bills (overhead, tools, insurance, profit). Parts are a band from budget aftermarket to the manufacturer part. Full method.
Not a repair shop, estimates only. Typical range, estimate. Not a quote. Your car, parts and shop change the number.
This is the range for the most common fix, oxygen sensor replacement (one sensor). Which repair your car needs depends on a proper diagnosis.
The oxygen sensor before the catalytic converter should flip between rich and lean several times a second. On cylinder 1's side it is switching too slowly. An aging sensor, coated with deposits, reacts late, so the computer cannot fine-tune the mix as quickly as it needs.
- Safe to drive?
- Usually yes, for now
- Most common cause
- Worn-out oxygen sensor
Safe to drive; mileage may suffer slightly.
What you may notice
- Check-engine light on
- Slightly worse fuel economy
- Possible mild hesitation
Common causes, most likely first
- Worn-out oxygen sensor
- Exhaust leak
- Fuel or oil contamination of the sensor
- Wiring issue
- Rich or lean running
Check this first
Think about the car's mileage. Sensors past 100,000 miles often slow down. Also ask the shop to check for exhaust leaks near the sensor and read the live data before replacing it, so the fix targets the right cause.
Other repairs that sometimes fix P0133
| Repair | Typical range, Boston |
|---|---|
| Diagnostic scan (check engine light) | $60 to $290 |
| Vacuum leak repair | $100 to $530 |
Before you pay
- Ask the shop what test showed this part is the cause, not just that the code appeared.
- Ask for parts and labor listed separately, and for the hours.
- Ask for a written OK before any extra work. Massachusetts rules require written authorization before repairs.
Got a quote already? Check it against the range. Want to see if your car has a recall tied to this problem? Check recalls by VIN.
Need to read a code yourself? OBD-II scanners on eBay (affiliate link, disclosure).
P0133 questions
Why does sensor age matter?
Over time, soot, oil and other deposits build up on the sensing tip, so it responds more slowly. Heat cycles also wear the element, so a sensor on a higher-mileage engine is more likely to be sluggish.
Can fuel additives help?
No. Fuel additives do not clean an oxygen sensor in any lasting way. Replacing the sensor is the reliable fix, and it is usually a modest job on most cars.
Is it an emissions item?
Yes. A slow sensor makes the computer adjust the mix late, which can raise emissions and cause a failed emissions test. It also costs a little fuel economy over time.
How much does it cost to fix P0133?
The most common fix, oxygen sensor replacement (one sensor), has a typical range of $110 to $370 in Boston. It is an estimate built from parts prices and local labor wages, not a quote. Your car and shop change it.
Related codes
- P0134: Oxygen sensor not responding (bank 1, before converter)
- P0131: Oxygen sensor reads low voltage (bank 1, before converter)
- P0171: Engine getting too much air or too little fuel (bank 1)
- P2196: Oxygen sensor stuck rich (bank 1, before converter)
More emissions codes
Code meaning written in our own words. Some codes mean different things on different makes, so check your scan tool or manual. Not a repair shop, estimates only.