Learn to develop your own strategic diagnostic routines to test circuits, components and control modules based on fully understanding wiring diagrams and circuit operation. Test these systems dynamically instead of the old static routines utilized by automotive manufactures that lead you in circles and then request “replace with known good components and retest”.
Learn to utilize non-intrusive test procedures as to not disturb connections that could in fact be the problem with the circuit. Old static test procedures often will temporarily alter the condition that is causing the intermittent.
Come sharpen your diagnostic skill set by fully utilizing wiring diagrams, the circuit road map.