P0133 fault code: what it means

P0133: Bank 1 upstream O2 sensor is slow to respond to mixture changes.

Engine and gearbox (powertrain) · Minor

Usual causes, most likely first

aged or contaminated front O2 sensor
exhaust leak before the sensor
intake air leak or PCV fault

P0133 by make

BMW

Front oxygen sensor slow response, bank 1. BMW lambda faults can be the control (rear) probe making the front one look bad.

Usual causes: ageing front oxygen sensor; exhaust leak before the sensor; rear control probe fault

Haval

Front O2 sensor slow response.

Usual causes: aged front O2 sensor; exhaust leak; wiring

Mazda

Front air-fuel (A/F) sensor slow to respond on SkyActiv-G. Usually an aged sensor; check for exhaust leaks near it.

Usual causes: aged front A/F sensor; exhaust leak near the sensor; sensor wiring or connector

MG

Front O2 sensor slow response.

Usual causes: aged front O2 sensor; exhaust leak; wiring

Mini

Front oxygen sensor slow response.

Usual causes: ageing front oxygen sensor; exhaust leak before the sensor; wiring or connector fault

Suzuki

Front O2 sensor slow response.

Usual causes: aged front O2 sensor; exhaust leak; engine running lean or rich

What the repair usually costs

Air-fuel ratio / front O2 sensor replace (upstream)NZ$270–NZ$750 · A$260–A$730
O2 sensor replace (downstream / after cat)NZ$180–NZ$480 · A$180–A$460

Not sure what P0133 means on your car? Ask Credov.

Before you clear it

Write the code down or photograph the scanner first. A code that comes straight back after clearing points to a fault that is still there. A car whose codes were cleared just before you arrived may be hiding one: the scanner's readiness monitors show "not ready" for a while after codes are cleared.

Researched by Credov from manufacturer and workshop sources. A fault code points to where a fault may be; a workshop confirms it with a diagnosis. Browse all fault codes.