Ok so today i went to get my new DD a smog test. But the day before put in a new stero that I had. And when I when up to get a smog test the smog machine didnt read the car? The man who worked there said i might of been my fault because of the stereo. Does anyone know how to fix this. Please help me out asap. thanks

 

sounds like when you installed the stereo you unhooked the battery which resets the ecu , on obd2 and up cars you have to long a certain amount of miles so the smog machine can scan the ecu i believe its 300 miles you have to log

 

Remove all the wiring for the stereo and see if they can communicate with the car. It's possible you tapped into on of the wires and it is shorted.