Fortuner rough running exhaust smell

I had a similar issue with my Fortuner. Check engine light, rough running, the whole bit. Is the smell really strong? Could be the catalytic converter failing too.

Yes, the exhaust smell is quite pungent. If it is the catalytic converter, wouldn't it be very expensive to repair? Could it still be a malfunctioning lambda sensor causing that smell?

Could be, but the smell being that strong is concerning. To be sure it's not the catalytic converter, take it to a workshop. It's better to diagnose it properly before replacing parts randomly.

Thank you for your advice. I took it to a mechanic, and after the diagnostic, they confirmed it was indeed a defective lambda sensor. The repair cost 375€. The check engine light is now off, and the engine runs smoothly.