400E does have a equivalent fuse, but it dosen't have an OVP relay, the fuse is one of the four fuses in the computer compartment. It protects ABS circuit & throttle controller & Cruise control unit.
When that fuse is opened, you will have ABS warning light on all the times, cruise control won't work and your engine rpm won't pass 5500rpm. This happened to me once, 50 cents for a 10 amp fuse solved three big problems, this was the most successful repair I have ever done on my cars.
In your case, that fuse should be OK, since you ABS is still functional, but you can try to replace all the other three fuses since they are cheap. I can't explain your fast idle problem, because myself is experiencing some erratic idle when cold also.
99 BMW 540i 6-speed 110K Km
03 SAAB 9-5 wagon 80K Km
92 400E (Sold) 245K km
Still missing the days with the Benz, it kept me busy.