Scenic engine control malfunction

Engine control malfunction on a Scenic that age could be a few things. First, double-check those battery cable connections; corrosion can be sneaky. Clean them thoroughly and make sure they're tight. After that, have you had the ECU scanned for any fault codes? That's the first step in diagnosing an ECU issue. It could also be a problem with the engine software, although that's less common.

Thanks! When you say 'scan the ECU', is that something I can do myself, or do I need special equipment? Also, what am I looking for when checking the battery connections? Is there a specific voltage I should be seeing?

Scanning the ECU requires an OBD2 scanner, which you can buy relatively cheaply online, or your local workshop will have one. If you aren't comfortable using one, I suggest you pay them a visit. The fault code will tell you where to start looking. As for the battery, it's not so much voltage as ensuring you have a clean, solid connection. Corrosion causes resistance. Given the age, it's probably best to get it looked at by a professional.

Okay, I took your advice and brought it to a local mechanic. Turns out the battery connections weren't as good as I thought – they were corroded underneath. Cleaned them up and it started right away. Cost me 155€ for the diagnosis and cleaning. Thanks for the help!