355 Alarm keeps going off on F355

Alarm keeps going off for no reason. It’s on a trickle charge 24/7 until I drive it. Was at work the other day and the wife told me the car alarm seemed like it was beeping. And its more like a beeping than the horn and loud. Does the horn sound when the alarm is tripped or is it more of a beeping sound. Got home and car was locked and with no sign of entry. What triggers the alarm? Does a door have to be opened. Maybe the battery is going bad?


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Usually caused by anti lift sensor. SD1 or 2 can quickly diagnose.

 

Have you actually heard the sound yourself, or just your wife? Would you be able to record it?

This type of Bosch Immobiliser is the same model as used on the Ferrari 550 and (on the 550) it does have an input to the horn relay, but I've pored over the F355 wiring diagrams and I haven't been able to find a link between the Immobiliser ECU and the horn (at least not on USA cars). (EDIT) Standby... I've just found a diagram on the '96 car which shows a link to the horn. I don't know if this is on all F355's

To hear what the alarm siren sounds like, arm the alarm and then activate the battery kill switch. It's loud, not a beeping sound. What your wife is describing sounds more like a seatbelt warning or convertible roof open warning. Quite possibly, an old battery might be triggering this beeping. Do you know how old it is?

When you arm the alarm, what happens to the LED on the dash? What happens to the LED when you disarm the alarm?

 

To get a full picture of the alarm system, you need wiring diagrams for exterior lights, engine management, suspension, windows and doors over several years and models, and just when you think you've figured it out, you find the wiring on your car disagrees with the official Ferrari wiring diagrams

Here's my latest Ferrari F355 (5.2) immobiliser diagram, but as stated, other diagrams are required to get a full picture:

5.2 Immobiliser/alarm System

 

Anti lift sensor for sure. Mine drove me nuts!!! middle of the night and day. I did a 360 lift sensor conversion on mine havn't heard the alarm since unless i set it off

 

Hey guys. I think my 355 anti-lift might be going as well. Yesterday the alarm started triggering multiple times for no reason with the car sitting in the garage. I've checked to ensure everything is closed so nothing should be setting it off. I'm going to try swapping out the sensor... but I can't tell where it is located from any of the ricambi diagrams. Google didn't help either. Can someone who knows tell me where it's located?

 

It's near the battery cutoff switch in the forward luggage compartment. You'll need to remove the liner. Be careful, that liner is very fragile.

 

Thanks, Q! I'll take a look.

And I've pulled the liner before, so yeah, I've dealt with it, but thanks again for the heads-up and all the other info you've collected and shared on the immobilizer.

 

In my case it was the battery in the alarm/siren itself. I replaced it rather than open it up find a compatible battery and then glue it back together and all that mess. My brother and I put it in about 30 minutes. You have to take the front left wheel off and some plates underneath. At the time Scuderia Parts has them on sale so it worked out.

 

I see Gobble is offering some 355 sirens on the 'for sale' forums (reprogrammed Corvette units), but only the sirens with separate adaptor leads.

https://www.ferrarichat.com/forum/threads/new-sirens-for-355-360-456-550-575.625850/

 

I have a strange addition to this problem - my alarm is intermittently going off (let’s say the lift sensor is the culprit) when the car is locked. I unlock it to stop the beeps and leave the car. Within a few minutes the car has locked itself again and the beeps start! I didn’t know the F355 self locks!

 

I didn’t know, either. I can’t say I’ve had this happen to my car. I’m wondering if you have a doorlock issue or a combination of issues. Fortunately, the 355 door lock system is not as complicated as the later cars or V12s.

When you arm or disarm the alarm with the fob, do you get the right number of chirps? Does the LED go out when you disarm the alarm? Does the LED flash normally when the car is locked?

Do you know if your car has the old type “barrel” shaped motion sensor? I bought the upgrade kit in case my old type failed, but I haven’t needed to fit it yet. I can’t say I’ve heard of the new type failing.

 

I forgot you’d also posted here with lots of extra information:

https://www.ferrarichat.com/forum/threads/unusual-f355-alarm-issue.691871/

Maybe we should stick to the one thread.