Simply turning off the check engine light in your 2004 Volkswagon Jetta will not allow it to pass the smog test. When the light is reset any stored codes are cleared and the "monitors" are reset. The "monitors" must be run again before the smog test will pass. Your best option would be to have the check engine light issue diagnosed and repaired. Please read the following RepairPal article for more information - http://repairpal.com/drive-cycle-emissions-readiness.