Peugeot 307 Fault Codes

It's possible. Have you used a diagnostic scanner to pull the specific fault code? Knowing the exact code would help narrow down the possibilities. Did you recently change any control modules?

Yes, I used a diagnostic scanner, but there are multiple codes. Would resetting the codes with an OBD-II scanner be a useful next step, or is that likely to just mask the underlying problem?

Resetting might temporarily clear the messages, but if the underlying coding is the issue, the errors will likely return. Given the symptoms and mileage, incorrect coding is a strong possibility. I suggest a workshop visit.

Thanks, I appreciate the advice. I took it to a shop, and you were right – the coding was off. Recoding cost 360€. Everything's running smoothly now.