Greetings, Ive had my X350 a few months now, the horn does not work and when the ambient air temp is above 60 and I ve driven the car for over over 45 minutes, when I restart, it sputters and hesitates a minute then settles in and I can drive it perfectly fine after. Sometimes when this happens I get check engine light and several codes about nearly all cylinders having a misfire. I took to my mechanic who went through and discovered the horn relay and EMS relay(and many others) reside on the same circuit board (soldered in...not replaceable) in the front fusebox in engine bay. He thinks there may be a hairline crack or something that is causing both issues. Seems logical to me but before I spend big bucks on a new fuse box, was wondering if anyone else has had similar issues or any other ideas.

Thanks!!

 

If the horn isn't working, it should be fairly easy to definitively diagnose the cause without guessing. If the mechanic suspects the horn relay, then he should be able confirm power is being applied to the input side of the relay and that no power is coming out the output side.


I recently had a hot restart issue very similar to what you describe. Restarting the car after letting it sit for 15-20 min, after it had been driven long enough to reach normal operating temps was causing the car to sputter, hesitate and generally run very rough for the first 10-20 seconds, at which point it would smooth out and run perfectly again. An engine code was set after a number of these events. I don't know what the engine codes were. In my case it was an air intake leak.

 

Well.. it could be what the mech says but did both faults occur at the same time?

Usually it would be 2 unconnected faults. Horn can't be hard to figure. The other is more serious - start by suspecting the battery (load test) and checking for air leaks (watch fuel trims).