P0133

O2 Sensor Circuit Slow Response Bank 1 Sensor 1

Fuel & air metering (O2 sensor) Generic OBD-II Medium

What it means

P0133 means the upstream oxygen sensor on bank 1 is switching between rich and lean too slowly. This sensor feeds the ECM's fuel control, so a lazy response worsens fuel trim, economy, and emissions. It's almost always an aged sensor. The car drives fine, but the sensor should be replaced before an emissions test.

Medium

Can I keep driving? Yes — the car drives normally, but fuel trim and economy suffer and it will fail emissions, so plan to replace the sensor soon.

Real-world scan data

Seen in

2,138

scans in the past year

Found in

0.3%

of scans

0.6%

of scans that found faults

Appears alongside · share of P0133 scans

P0171in 44.1% of scans

P0130in 40.9% of scans

P0420in 39.0% of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

Check-engine light on
Reduced fuel economy
Slightly rough or uneven idle in some cases
Failed emissions test

Common causes

Most likely first

Aged or contaminated upstream oxygen sensor switching too slowly — the most common causeLikely
Exhaust leak upstream of the sensor skewing readingsCommon
Damaged wiring or a poor connector at the sensorCommon
Silicone or coolant contamination of the sensor elementLess often
Rarely, a faulty ECMLess often

How to diagnose & fix

Work through it in order

Read freeze-frame data and view the bank 1 sensor 1 waveform on a scan tool — a slow, lazy switch confirms the code.
Inspect the upstream exhaust for leaks and check the sensor's connector and wiring.
If the sensor is original or high-mileage and switching slowly, replace the upstream O2 sensor.
Clear the code and re-drive to confirm the sensor now switches quickly.

FAQ

Quick answers

Is it safe to drive with P0133?+

Yes, in the short term. The engine still runs, but a lazy O2 sensor hurts fuel trim and economy and will fail an emissions test, so don't put it off.

Can I just clear P0133?+

It comes back after the O2 monitor re-runs unless the sensor or exhaust leak is fixed.

Read & clear P0133 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX