Can a vacuum leak cause P0133?

Yes. Unmetered air from a split hose, a leaking intake gasket or a faulty PCV valve upsets the mixture the engine computer uses as its reference, and the sensor can then appear slow. A leak big enough to do this usually sets a lean code such as P0171 as well, so if P0133 appears with P0171, look for the air leak before replacing the sensor.

Will P0133 clear itself?

The warning light can go out on its own after several drive cycles in which the slow-response test passes, but that does not mean the fault is fixed. A sensor that is close to the limit tends to fail the test again, and the code returns. Clearing the code without a repair also resets the readiness monitors, which can stop the car passing an emissions check until they have run again, depending on the country's rules.

Is P0133 always the oxygen sensor?

The sensor is the most common cause, especially one that has covered a high mileage or been exposed to oil or coolant. But an exhaust leak ahead of the sensor, an intake air leak, a weak heater circuit or a poor ground can all make a good sensor look slow. Rule those out first, because a new sensor will not fix them and the code will come back.

Why does my Toyota show P2A00 instead of P0133?

Many Toyota engines use an air-fuel ratio sensor instead of a switching oxygen sensor in this position, and Toyota's repair manuals report the equivalent slow-response fault on those engines as P2A00, 'A/F Sensor Circuit Slow Response (Bank 1 Sensor 1)'. The diagnosis is similar: check for exhaust and intake leaks and the sensor's wiring before replacing the sensor.

How much does it cost to fix P0133?

A replacement narrowband sensor costs about €80 to €270 fitted at an independent workshop, and a wideband sensor of original-equipment quality about €150 to €400. If the real cause is an intake air leak, the repair is typically €50 to €210, and an exhaust leak at the manifold gasket roughly €80 to €300.

P0133: O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)

Quick Answer

Safe to drive (short-term)

P0133 means the upstream oxygen sensor on bank 1 (before the catalytic converter) still produces a signal, but it reacts too slowly when the mixture changes. The engine computer times how quickly the sensor follows its own rich and lean fuel corrections and sets the code when the response is too sluggish. An aged or contaminated sensor is the usual cause, but an exhaust leak, an intake air leak or a weak sensor heater can produce the same result.

Severity: Moderate · Emissions
Estimated repair cost: From €45 to €400+, varies by vehicle

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What does P0133 mean?

P0133 is a emissions-related diagnostic trouble code classified as moderate severity. When your vehicle's ECU detects this condition, it stores P0133 and illuminates the check engine light.

Where it is on the car

Engine
Oxygen sensor before the converter (sensor 1)
Catalytic converter
Oxygen sensor after the converter (sensor 2, or 3 on some cars)
Silencer and tailpipe

What are the symptoms of P0133?

If your vehicle has triggered P0133, you may notice one or more of these symptoms:

Check engine light on, usually with no obvious change in how the car drives
Gradually worse fuel economy
Slightly unstable idle once the engine is warm
Failed emissions check, or an oxygen sensor readiness monitor that will not complete
Faint sulphur smell from the exhaust
Code that clears itself for a few days and then returns

What causes P0133?

Here are the most common causes of P0133:

Aged or contaminated upstream oxygen sensor, with deposits from oil burning, coolant or silicone slowing its reaction
: high
Exhaust leak ahead of the sensor diluting the exhaust sample with outside air
: medium
Intake air leak or crankcase ventilation (PCV) fault adding unmetered air
: medium
Weak sensor heater or heater circuit fault leaving the sensor below its working temperature
: medium
Wiring or connector fault, such as a high-resistance ground or corroded pins
: low
Fuel delivery or MAF sensor problem upsetting the mixture the sensor is timed against
: low

Is it safe to drive with P0133?

Generally yes, for short-term driving. Safe to drive to a workshop. In most cases the engine runs normally, but fuel control is less precise, so fuel use and emissions creep up, and it is the kind of fault that can get a car rejected at an emissions check, depending on the country's rules. It is not an emergency, but a slow sensor can hide a developing mixture problem, so plan the repair within a few weeks. If the check engine light starts flashing, stop and get it checked.

How do you diagnose P0133?

Follow these steps to pinpoint the root cause of P0133:

Read every stored code and the freeze frame. Fix lean or rich fuel trim codes, misfires, MAF faults and oxygen sensor heater codes first, because each of them can make a healthy sensor look slow
Find out whether your engine has a narrowband or a wideband (air-fuel ratio) sensor in this position, because the two behave very differently on a scan tool
On a narrowband sensor, hold a fully warm engine at 2,000 to 2,500 rpm and watch the signal. It should swing several times a second between below 0.2 V and above 0.8 V, with quick transitions. A lazy, rounded wave with few swings fits P0133. A generic OBD2 reader samples too slowly to judge switching speed precisely, so treat what you see as a rough guide; a lab scope or the manufacturer's software shows it properly
On a wideband sensor, snap the throttle open and closed on a warm engine and watch the lambda value: it should move promptly toward rich and then lean. A reading that drifts slowly back to 1.00 supports a slow sensor
Check for exhaust leaks ahead of the sensor (ticking at the manifold on a cold start, soot trails at the gasket) and for intake leaks with a smoke test, including the PCV valve and its hoses
Check the sensor heater: the fuse, the heater resistance across the heater pins with the sensor unplugged, and the heater feed voltage with the key on
If everything else checks out, replace the sensor with one that matches the original part number, clear the code and drive a full warm-up cycle. The oxygen sensor monitor result appears in the readiness status, and on many cars in the Mode 06 test results, once it has run

How much does P0133 cost to fix?

Repair costs for P0133 vary depending on the root cause and your vehicle. Here are typical estimates:

Repair	Parts Cost	Labor Cost	Total Estimate	DIY Difficulty
Replace upstream O2 sensor (bank 1 sensor 1), narrowband type	€30–€150	€50–€120	€80–€270	Moderate
Replace upstream wideband (air-fuel ratio) sensor, OE quality	€100–€280	€50–€120	€150–€400	Moderate
Fix intake vacuum leak (hose, clamp or PCV fault)	€10–€60	€40–€150	€50–€210	Moderate
Repair exhaust leak at the manifold gasket or studs ahead of the sensor	€20–€100	€60–€200	€80–€300	Moderate
Repair O2 sensor wiring or connector	€5–€25	€40–€120	€45–€145	Moderate

Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.

Full repair guides

Oxygen Sensor Replacement Cost

P0133 on specific vehicles

P0133 behaves differently depending on your vehicle. Select your car below for model-specific causes and known issues:

P0133 on Volkswagen

Volkswagen Golf

See Volkswagen-specific causes & cost

P0133 on Nissan

Nissan Qashqai · Nissan Altima

See Nissan-specific causes & cost

These codes are often seen alongside P0133 or indicate related issues:

Common questions about P0133

What does P0133 mean?: P0133 means the upstream oxygen sensor on bank 1, the sensor before the catalytic converter, is responding too slowly to changes in the mixture. The engine computer deliberately swings the fuelling slightly rich and lean and measures how fast the sensor follows. When the sensor lags beyond the limit, the code is stored and the check engine light comes on.
Can a vacuum leak cause P0133?: Yes. Unmetered air from a split hose, a leaking intake gasket or a faulty PCV valve upsets the mixture the engine computer uses as its reference, and the sensor can then appear slow. A leak big enough to do this usually sets a lean code such as P0171 as well, so if P0133 appears with P0171, look for the air leak before replacing the sensor.
Will P0133 clear itself?: The warning light can go out on its own after several drive cycles in which the slow-response test passes, but that does not mean the fault is fixed. A sensor that is close to the limit tends to fail the test again, and the code returns. Clearing the code without a repair also resets the readiness monitors, which can stop the car passing an emissions check until they have run again, depending on the country's rules.
Is P0133 always the oxygen sensor?: The sensor is the most common cause, especially one that has covered a high mileage or been exposed to oil or coolant. But an exhaust leak ahead of the sensor, an intake air leak, a weak heater circuit or a poor ground can all make a good sensor look slow. Rule those out first, because a new sensor will not fix them and the code will come back.
Why does my Toyota show P2A00 instead of P0133?: Many Toyota engines use an air-fuel ratio sensor instead of a switching oxygen sensor in this position, and Toyota's repair manuals report the equivalent slow-response fault on those engines as P2A00, 'A/F Sensor Circuit Slow Response (Bank 1 Sensor 1)'. The diagnosis is similar: check for exhaust and intake leaks and the sensor's wiring before replacing the sensor.
How much does it cost to fix P0133?: A replacement narrowband sensor costs about €80 to €270 fitted at an independent workshop, and a wideband sensor of original-equipment quality about €150 to €400. If the real cause is an intake air leak, the repair is typically €50 to €210, and an exhaust leak at the manifold gasket roughly €80 to €300.

Read our detailed guides

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