Replace 360 Modena Motronic ECU??

No, you do not have to replace both. The LH and RH units are interchangeable. If your alarm ecu has ever been changed though, you may have an issue doing another swap on the Motronics. The alarm immobilizer code is burned in once they're swapped and it is burned in on the right side Motronic. It's a complicated issue, but hopefully you'll be o.k.

C-

 

I would just replace the LH unit, if that one was bad. I had you swapping the unit on the previous post, but you do not need to do this since the alarm is communicating with the RH Motronic. Be aware a new Motronic is about $2,500.00 new.

C-

 

I own a 348 and don't have direct experience with a 360. But if one of my ECUs malfunctioned, the first thing I'd try would be to disconnect the battery to de-power the ECU, and then restart the car and let it run for 15min or so to allow it to reset. That is, if you're not absolutely sure the ECU has a definite failure. I would think the 360 manuals would have a procedure similar to the 348 outlined. If you can't restart the car after using the procedure, either the ECU or something else is wrong. At least worth investigating before spending big $ on a new ECU, unless you're sure it's bad.