Oxygen (lambda) sensors

P1133 Air/fuel ratio sensor slow to respond (bank 1, sensor 1)

By: Diagno editorial team · Updated: 2026-10-15

P1133 means: Air/fuel ratio sensor slow to respond (bank 1, sensor 1). The oxygen sensor measures oxygen in the exhaust and the computer sets the fuel mixture by it. OK to drive, but have it checked soon. The repair usually costs about €60–300 in Estonia.

Is it safe to drive?OK to driveOK to drive, but have it checked soon.

Typical repair cost€60–300parts and labour in Estonia

What it means

The oxygen sensor measures oxygen in the exhaust and the computer sets the fuel mixture by it. Sensor 1 sits before the catalytic converter, sensor 2 after it. The computer found the signal wrong, slow or missing.

This is a make-specific code (Toyota). The exact meaning can vary by model and year. On other makes the same code means: GM: Oxygen sensor switches too rarely (bank 1, sensor 1).

What you may notice

Engine light on
Higher fuel consumption
Idle may be uneven
Emissions may fail the inspection

What could be wrong

1Old or faulty oxygen sensor
2Exhaust leak ahead of the sensor
3Damaged wire or connector
4The mixture really is off (air leak or injector)

Repair difficulty: Moderate

What you can check yourself

Listen for an exhaust leak ahead of the sensor. Check that the sensor wire is intact and the connector is clipped in. You can do the simpler checks yourself.

How we fix it

We check the sensor signal and fuel trims on the diagnostic tool
We check for exhaust leaks
We replace the oxygen sensor if it is old or slow

Standard SAE description: A/F Sensor Circuit Response (Bank 1 Sensor 1)

This code usually comes with: Check engine lightSee what the light means →

Want a definite answer?

Bring the car to our workshop in Estonia for diagnostics. We read the fault codes, test the sensors and tell you what is wrong. Repair price depends on the work involved, generally €45 per hour.

Book a diagnostic check

Questions

What does fault code P1133 mean?

Air/fuel ratio sensor slow to respond (bank 1, sensor 1). The oxygen sensor measures oxygen in the exhaust and the computer sets the fuel mixture by it. Sensor 1 sits before the catalytic converter, sensor 2 after it. The computer found the signal wrong, slow or missing.

Can I drive with code P1133?

OK to drive, but have it checked soon.

How much does it cost to fix P1133?

Roughly €60–300 in Estonia. The price depends on exactly what has failed and on the car.

How is P1133 fixed?

We check the sensor signal and fuel trims on the diagnostic tool. We check for exhaust leaks. We replace the oxygen sensor if it is old or slow.

Based on AI combined with our hands-on workshop experience and knowledge. This information is general and prices are approximate (Estonian workshop rates). The same code can mean different things on different cars. Only an inspection of the car gives a definite answer.