Emissions code
P0131: Oxygen sensor reads low voltage (bank 1, before converter)
How much to fix P0131? Typically $100–$350.
How this range is built
| Part of the job | Low | High |
|---|---|---|
| Parts | $40 | $180 |
| Labor: 0.6 to 1 hours × $110 to $150 an hour | $66 | $150 |
| Fees: shop supplies, disposal, diagnostics | $0 | $15 |
| Total, rounded | $100 | $350 |
The hourly rate is the BLS Occupational Employment and Wage Statistics, May 2025 average pay for this trade in the US, $27.13 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 in front of the catalytic converter on cylinder 1's side is sending low voltage, which normally means a lean mix with lots of air. It could be telling the truth because of an exhaust or vacuum leak, or it could be an aging sensor that has gone weak.
- Safe to drive?
- Usually yes, for now
- Most common cause
- Aging oxygen sensor
Safe to drive for a while; the engine may run slightly off.
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What you may notice
- Check-engine light on
- Poor mileage
- Hesitation
Common causes, most likely first
- Aging oxygen sensor
- Exhaust leak before the sensor
- Vacuum leak
- Wiring short
- Fuel delivery problem
Check this first
Listen near the exhaust manifold for ticking or puffing that goes away as the engine warms up, and look for black soot at the joints. A shop can also read live fuel trim values to see whether the engine is really lean.
Other repairs that sometimes fix P0131
| Repair | Typical range, US |
|---|---|
| Vacuum leak repair | $90 to $460 |
| Mass airflow sensor replacement | $120 to $390 |
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. Many states 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).
P0131 questions
Is the sensor bad or lying?
It might be accurately reporting a lean engine. Looking at fuel trims shows which. If trims are high, the problem is air or fuel, and the sensor may be innocent. If trims are normal, the sensor is the suspect.
Could an exhaust leak cause it?
Yes. A leak ahead of the sensor pulls in outside air, which makes the reading look lean. The fix is welding or replacing the gasket or pipe, not the sensor, so the leak check is worth doing first.
Do I replace both front sensors?
Not unless both are flagged. Each one has its own code, and the other one may still work fine. If both are very old, a shop may suggest it, but ask them to explain the reasoning.
How much does it cost to fix P0131?
The most common fix, oxygen sensor replacement (one sensor), has a typical range of $100 to $350 across the US. It is an estimate built from parts prices and local labor wages, not a quote. Your car and shop change it.
Typical range in 10 metro areas
Only the labor rate changes between cities. Same parts, same hours.
| Area | Typical range, estimate |
|---|---|
| Boston area, Massachusetts | $110 to $370 |
| New York City area | $110 to $360 |
| Los Angeles area, California | $110 to $370 |
| Chicago area, Illinois | $100 to $350 |
| Houston area, Texas | $100 to $340 |
| Dallas-Fort Worth area, Texas | $100 to $340 |
| Phoenix area, Arizona | $100 to $350 |
| Atlanta area, Georgia | $100 to $350 |
| Miami area, Florida | $100 to $350 |
| Seattle area, Washington | $110 to $370 |
Related codes
- P0133: Oxygen sensor responding slowly (bank 1, before converter)
- P0134: Oxygen sensor not responding (bank 1, before converter)
- P0171: Engine getting too much air or too little fuel (bank 1)
- P0135: Oxygen sensor heater fault (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.