Converted a 5 spd civic sedan to automatic. i replaced EVERYTHING. underdash wire harness and all. the car just clicks one time under the hood at start up. all starter connections are tight, battery is good, power accessories good, no CELs. Any ideas?

 

The one time clicking is very typical of battery connection problem. Quadruple check the battery terminals and the cable terminals are clean and all, it used to happen to me all the time, I had to screw in a little screw to make it nice n tight in the positive terminal. Good luck!

 

Check the grounds (the one on the tranny and ect.), i've seen this be the problem before and seeing as how you had them apart it may be a place to look.