Yesterday I pick-up my (European) F355 97 (36’000km) from the annual service (oil, …, not a big one with the distribution belt). In addition to the standard maintenance, the mechanical had to grease the by-pass valve who seams to remain closed. After driving only 2 km, I got the “Slow Down” warning light blinking. The water and oil temperature were quite normal (far below the red zone). The engine was running fine from cold to normal working temperature. I did not noticed any misfired, strange engine noise nor problem to revs the engine. I went back strait to the Ferrari garage who checked the error codes (from the 5.2 Motronic). Both left and right CATs where in error (overheating). No need to mention that I never had this problem before I brought the car to the service! This even when I used to be stuck in traffic jam (where the engine temp use to be higher). Since both the car outside as well as the plastics parts of the engine bay (ie. air filter, lateral shock absorbers panels protection, … ) has been washed by Ferrari, I wonder if I’m not facing an electrical problem. It’s effectively surprising to suddenly get both CAT in errors! I therefore rather suspect a false error caused by the system controlling the CAT (ie ECU). Could water have reached the electrical contact of the ECU, of the CAT sensor, … ? Does anyone have an idea of the possible cause of this “Slow down” overheated CAT problem? Thanks in advance. Christophe.