pulsating lights on 2001 Audi A6 Quattro

all of my lights are pulsating. i have replaced the alternator and battery. but i have a check engine light that as yet is unexplained. could this be the problem??

Asked by for the 2001 Audi A6 Quattro
Please post back and tell what the stored trouble codes are ie P0420, P1172 ect.... Check the basics first. Check the battery cables are clean tight and secure, heck engine and chassis ground. Check battery and alternator power cables are "good". Look on YOUTUBE search for voltage drop test. Voltage drops can cause all sorts of problems. Also is the alternator a good reputable rebuild.