Inconsistent Key Fob Performance

Is it just the siren chirp that is not working? Or the doorlocks, too?

Do you know if any of your fobs are cloned?

 

Seems like your FOB's may have been replaced at some point in the car's life with a clone and not properly synced to the ecu. What happens is the alarm ecu has a rolling code, so if a cloned FOB is made and not properly synced, then it will be on a different rolled code than the others, thus every time you press the button it will try the next code one by one until it reaches the correct code to arm/disarm. But then the other FOB's will be out of sync and it's a never ending cycle.

You should send a message to @gobble , he's everyone's go to for FOB related issues. He fixed my entire system perfectly, very highly recommended.

 

Try removing the battery and pinching the contacts together so the battery makes better contact. Then, while pinching the contacts against the battery, spin the battery to remove any corrosion. It is possible to have enough contact to make the LED illuminate, but not enough to send out a signal.

Since everything worked fine before, spread contacts are a good bet.

Best idea is to contact Mark (Gobble) at ferrarifobs.com and trade in your old set of fobs for a new set that uses 2032 lithium watch batteries. Those batteries last 5+ years and range seems to be increased, too. Love my new set. Or sell your old set after buying a new set. Old sets with PIN bring about $350 bucks with no effort.

 

Since the problem exists on both fobs it is not the fobs.
You need to check the antenna on the immobilizer.

 

My point is that, according to what you have said, since both fobs exhibit exactly the same symptoms the fault must lay elsewhere. I would first assume that the fob signal is not being received by the immobilizer. A quick search of "immobilizer antenna" mentions a red wire under the immobilizer on a 360.
I have no knowledge of the 550 immobilizer but I would assume it's similar to the 360 so I would start my search there.

I realize the above is based on assumptions but isn't that what a diagnostic procedure is?

https://www.ferrarichat.com/forum/posts/144774461/

Check the blue wire for possible loose connection, apply Detoxit to all Immobilizer connections then see if that cures the problem.

Amazon.com: DeoxIT 5% Spray Contact Cleaner, 5 oz.

 

It's a short piece of wire plugged into the Immobilizer ECU. The 456M experts should be able to help you find the ECU. The antenna is sort of held in place by some loose plastic clips, but it is possible that the antenna has slipped behind the ECU case and the case is blocking the signal.

 

This is all the WSM has on the location:

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You can see that the antenna wire is curled around item 8. Is it under the driver's seat or rear passenger seat?

Hopefully someone has accessed these components in the past on your car as they are normally under a riveted panel.

 

I didn't realize you had a 456M so try this instead of the 550 picture above

https://www.ferrarifobs.com/456-immobilizer-removal

 

Mirek- Reprogramming the Alarm ECU/Immobilizer to accept 3 new fobs is a 5 minute job. There are tons of videos on the subject, including a good one on Mark's site. And here is a document that explains how to do it with a checklist.