Nissan Repair: lights dim when brakes are hit, knock sensor, vaccum

Question
i think i have a ground problem but have checked out all connection and fuses.  add another ground from battery post to front fender no help.  batt light does come on when key is in acc position.  knock sensor looks bad maybe cause by bad ground?  check engine light is on

car is a pooch.  slow as a snail.  

Answer
i have a similar problem to mine.  your brakes are ran by vaccum and any sort of leak would cause the system to bog when you hit the brakes because your electrical is trying to compensate for the leak.  it would also explain your "slow as a snail" symptom.  what code is your check engine light throwing?  do a test on your ecu and pull the codes its storing.  if you can give me the year of your car and the make/model i will reply back with what codes you give me and let you know whats up with your vehicle.  but i would definatly check for leaks in the vaccum system for now.  my email is xxp_sebby@yahoo.com  good luck!