Meaning
The front lambda probe (bank 1, probe 1) switches between "lean" and "rich" more slowly than normal. The computer cannot control the mixture accurately.
Urgency
Low to medium. The car drives, but consumption and emissions increase, and over time the catalytic converter suffers.
It affects
Gasoline engines. Lambda probe, exhaust, mixture.
What does P0133 mean
A working front probe changes its signal several times per second. Over the years, it becomes covered with scum, "gets old" and reacts slowly. The computer measures how fast the shifting takes place and records P0133. if the response is too slow
Symptoms
- "Check Engine" lamp, often with no other apparent problem
- Slightly increased fuel consumption
- Rough idle in a more serious case
- Failed emissions technical review
| Can it be driven?
Yes. It's not urgent, but don't put it off for months — the incorrect mixture damages the catalyst (P0420).
Common reasons
- Obsolete lambda probe — the most common cause after a long run.
- Contaminated probe — from burning oil, antifreeze or a rich mixture.
- Exhaust leak in front of the probe.
- Vacuum leak or mixture problem (P0171, P0172).
- Wiring — corroded wire, oxidized coupling.
How we diagnose it
- We look at the probe signal in real time with the engine warmed up.
- We check the reaction to a sudden gas supply.
- We check the muffler for leaks and the wiring.
- If the engine burns oil — we look for the cause before changing the probe.