I have a 1992 honda accord and i just replaced the main relay due to problems with the car not starting on really hot days. Since ive changed the relay the D4 light stays lit and a clicking noise comes from the cockpit also its on limp mode. I was told to check the TCU which i did. there is no burnt out components on the circuit board. I cannot figure out this problem.. Can someone help me out???

 

Check the codes (CEL and D4), what do you have?

For giggles. Clean the battery cables, I'd also clean the "other" end of the ground cable - it contacts the body and then the trans.

Last, there is a ground on the t-stat housing as well, I'd pull and clean that.