Antipollution Error

While driving my Peugeot 307 1.6 XR, it gave me an anti-pollution warning light and the engine light turned on yellow. I took it to a mechanic, who connected it to the computer and said the solenoid valve needed to be replaced, and quoted me 9,000. I took it to another mechanic, who connected it to the computer and said we drove it twice, no problem, and then turned off the warning light on the computer. But before I even got home, the yellow light came on again. I'm going on a long trip in two days. Can you help me fix this error? :)

Hello sir, what was the error code? Is the vehicle diesel or gasoline?

Okay, friends, I took it to the LPG expert and he solved it for 50 liras. Thanks, it turns out to be due to the rich-lean fuel mixture.

I'm glad your problem is solved, sir. Thank you for the feedback. If your LPG kit is compatible with a 2 ohm LPG injector, it would be better to get a 2 ohm injector and adjust the AFR accordingly.