Peugeot 108 alarm siren fault

Sounds familiar! I've had similar signal problems with my 108, although the error codes were slightly different. Is it throwing any specific DTCs related to the alarm system? Check the connections to the siren unit itself. Also, did you recently change the battery? I know, it sounds weird, but a low voltage situation can sometimes trigger weird alarm faults. I was going nuts trying to fix it.

No battery change recently. The error memory just says 'siren communication fault'. Where exactly is the siren unit located? I'm guessing it's not easily accessible. I suppose the cable or plug connection could be defective, but I can't really check without knowing where to look.

Yeah, the siren is a pain to get to. On mine, it's tucked up behind the front wheel arch liner on the passenger side. You'll probably need to jack up the car and remove the wheel to get decent access. Given the error and the hassle of getting to it, honestly, I'd suggest taking it to a workshop. I eventually caved and paid them to sort it. Turned out to be a corroded connector, but they charged me an hour's labor to diagnose and fix. Could have saved myself some stress.

Thanks for the info. Workshop it is, then. The estimate I got was around 95€, so it seems like a reasonable price to pay to avoid messing with it myself. At least I know what the likely culprit is now.