they way to test a faulty relay is to get the car started. once running turn the key to off then back to acc. don't crank but turn it back to the on position.

do it very fast. if the car catches itself from dieing your relay is fine. if it doesn't catch itself relay is dieing.

if your cel is flashing six times it could be a code 6. search your model year and see what code 6 is. first play to start.

it shouldn't give you a code reading without jumping the connector. so i'm not sure what to tell you.

either way. i dunno how you got to the main relay being the culprit.