Peugeot 2008 won't start

Loose battery connections are definitely suspect! Has the engine been cranking at all or just completely dead? Any other weird electrical issues?

It's completely dead, no cranking at all. No other electrical issues that I've noticed, just the engine light. Should I try cleaning the terminals?

Sounds like a bad connection then. Cleaning the terminals is a good start, but if that doesn't fix it, get it to a workshop. Could be a deeper electrical problem that needs proper diagnosis.

Thanks for the advice! Cleaning the terminals and tightening the connections did the trick. Apparently, it cost me 155€. The engine started right up. I really appreciate the help!