_WELL IT just may be an under the dash wire short or connection, they can trace everything on th motor with the diagnostic computer but if its beyond the engine say a shorted wire in the dash or fuse box then you’ll just have to let them diagnose it. I once had a 58 Buick catch on fire so my mechanic got a whole wire harness and found the problem was the cigarette light er had a short. After that I never used a cigarette light in any car up till now , but its just that I quit smoking 29 years ago so I dont let any one smoke in my car or truck.