P0133 O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)
P0133 is a generic OBD2 powertrain code. It means “O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)” — the same on every make and model, because the definition comes from the SAE J2012 standard rather than from the carmaker.
Ask the AI about P0133 on your car- System
- Powertrain (P)
- Code type
- Generic (SAE)
- Range
- P01xx
- Urgency
- Low
What P0133 means
The upstream oxygen sensor on bank 1 should flip between rich and lean several times a second. The computer measured it switching too slowly: the sensor is ageing, or something is contaminating it.
Symptoms
- Usually nothing but the lamp
- Worse fuel economy
- Sometimes a catalyst code later (P0420/P0430)
Most likely causes
- An aged sensor — common past 100,000 miles
- An exhaust leak ahead of the sensor
- Contamination from oil, coolant or silicone sealant
- A fuel-mixture problem the sensor is only reporting
What to check first
- Fix any fuel-trim, misfire or exhaust-leak codes first
- Check for exhaust leaks around the manifold
- Replace the sensor if it’s old — the one for bank 1, sensor 1
Can I keep driving with P0133?
Safe to drive — fix it when convenient
Yes. Fix it within weeks: a slow sensor makes fuel control sloppier and can eventually harm the catalytic converter.
What the wording tells you
“Slow response” means the sensor still works but reacts to changes too slowly — typical of an ageing or contaminated sensor.
Bank 1: engines with two rows of cylinders — V6, V8, boxer — have two banks. Bank 1 is the side that holds cylinder 1, bank 2 the other side; an inline engine has only bank 1.
Sensor 1: exhaust sensors are numbered along the exhaust flow. Sensor 1 is the one nearest the engine — for oxygen sensors, the one before the catalytic converter — and each higher number sits further downstream.
How P0133 breaks down
Powertrain. Engine, transmission, fuel and emissions — the codes behind the check engine lamp.
Generic code: defined by SAE, the same on every make.
Fuel & air metering.
The specific fault within this range.
Where to look: Fuel & air metering
The sensors the engine computer meters fuel from — mass air flow, manifold pressure, intake air and coolant temperature, throttle position, oxygen sensors and fuel pressure — the fuel trims it learns from them, and the injector, fuel-pump and turbocharger circuits.
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Read and clear P0133 on your iPhone
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Frequently asked
What does P0133 mean?
P0133 is a generic OBD2 powertrain code. It means “O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)” — the same on every make and model, because the definition comes from the SAE J2012 standard rather than from the carmaker. The upstream oxygen sensor on bank 1 should flip between rich and lean several times a second. The computer measured it switching too slowly: the sensor is ageing, or something is contaminating it.
Can I drive with P0133?
Yes. Fix it within weeks: a slow sensor makes fuel control sloppier and can eventually harm the catalytic converter.
What causes P0133?
An aged sensor — common past 100,000 miles; An exhaust leak ahead of the sensor; Contamination from oil, coolant or silicone sealant; A fuel-mixture problem the sensor is only reporting.
How do I clear P0133?
Fix the cause first, then clear it with any OBD2 scanner or app. Once the fault is gone the car also clears it on its own: the check engine lamp goes off after the self-test passes on three drive cycles in a row, and the stored code ages out after about 40 warm-ups. Clearing without a repair only hides it for a while — and resets the readiness monitors an emissions inspection looks at.
Is P0133 the same on every car?
Yes. P0133 is a generic SAE J2012 code, so its definition is identical on every make and model. What differs is the cause behind it and the repair procedure, which depend on the engine — that’s why the assistant on this page asks for your car.
Guides
Definitions: the generic SAE J2012 codes from Brimly’s offline dictionary (data version 2026.09). Causes and advice are general guidance for all makes — the service information for your car has the last word.