I ran into a problem after installing a sound system in my car. my tach was working fine but after installation it didnt anymore. I was foolin around with the positive battery cable during install, I figured I fried the tach filter or something,so I ordered a new one but it still doesnt work. guage moves a little like its working some but will soon fall to 000. my question is could something have went wrong within the coil while messing around with battery cable. I think tach gets signal from coil. Is there a way to check coil for signal. car runs fine and shows no codes.:

my question is could something have went wrong within the coil while messing around with battery cable.

Highly unlikely seeing as the engine still runs which would indicate the coil is still good .More likely you screwed something up while up were under the dash; loose wire, dislodged connector somewhere?

:goodpost: I have found that a few of the issues that I have had over the years has been the result of my own hands touching something inadvertently!