Emission codes
P0133: oxygen sensor slow response (bank 1 sensor 1)
The upstream oxygen sensor should swing quickly between rich and lean readings as the engine computer trims the fuel. P0133 means the swing has become sluggish, so fuel control works with stale information.
P0133: can I drive, and what will the labor cost?
Estimated labor, replace upstream oxygen sensor (bank 1 sensor 1)
$33 to $110
| Labor time (estimate) | 0.3 to 1 h |
| Rate used | $110/h |
| Technician wage, United States (average) | $27.13/h |
| Moderate: fix within weeks Drivable; fuel control is less precise, which costs mileage and, over months, can wear the catalytic converter. | |
Labor only: parts and the diagnostic fee are not included. Hours are our estimate for a typical car; book times vary by model. Wage: BLS, May 2025.
P0133 is the generic OBD-II code for "O2 sensor circuit slow response, bank 1 sensor 1". Sensor 1 is the upstream sensor, ahead of the catalytic converter, whose signal the engine computer uses to keep the air-fuel mixture right. A healthy sensor switches between about 0.1 and 0.9 volts several times a second at steady speed; the computer measures how fast it moves and sets P0133 when the transitions take too long. Age is the most frequent cause, because the sensing ceramic slowly loses its response over tens of thousands of miles. An exhaust leak ahead of the sensor, which pulls in outside air and blurs the reading, comes next, together with contamination from coolant, oil or silicone sealant. A wiring fault is less frequent. The car is drivable, but imprecise fuel control costs mileage and, over months, can hurt the catalytic converter.
Is this repair still under the emission warranty?
Catalytic converter
Likely covered: ask a dealer
| Federal emission warranty, 8 years or 80,000 miles | within |
Age counts from delivery to the first buyer; whichever limit comes first ends the warranty. Your warranty booklet lists the covered parts and prevails.
Codes, rules and labor data checked by Radif Partners · Editorial policy · Method and sources
P0133 at a glance
| Code | P0133 |
| Standard description | O2 Sensor Circuit Slow Response (Bank 1 Sensor 1) |
| System | Oxygen sensors |
| Severity | Moderate: fix within weeks |
| Common symptoms | usually none, lower fuel economy, emissions test failure |
Sensor 1 and sensor 2
Most cars have at least two oxygen sensors per exhaust bank. The one before the converter (sensor 1) controls fuel; the one after (sensor 2) checks how well the converter is working. P0133 concerns the first. Replacing the downstream sensor by mistake is a classic waste of money, so check the location on the exhaust before ordering. On a V-shaped engine, bank 1 is the side with cylinder 1.
What contaminates a sensor
A white or chalky tip suggests coolant, often from a leaking head gasket; black, oily deposits point to oil burning; a shiny glaze can come from silicone sealant that was not rated for oxygen sensors. In those cases a new sensor will fail again unless the source is fixed, which is why a shop looks at the old part before ordering a new one.
Leaks first
A cracked manifold or a leaking gasket ahead of the sensor lets air in on each exhaust pulse, especially at idle. It also causes ticking noise when cold. Fixing the leak can cure P0133 on its own. If P0135 is stored too, the heater has failed and the sensor is cold, which also slows it down.
Likely causes of P0133, in order
| Cause | How often |
|---|---|
| Aged upstream oxygen sensor | most frequent |
| Exhaust leak ahead of the sensor | frequent |
| Sensor contaminated by coolant, oil or silicone | frequent |
| Wiring fault | less frequent |
P0133 repairs and labor time
| Repair | Labor (estimate) | At $110/h |
|---|---|---|
| Replace upstream oxygen sensor (bank 1 sensor 1) | 0.3 to 1 h | $33 to $110 |
| Repair exhaust leak ahead of the sensor | 0.5 to 1.5 h | $55 to $165 |