When I plug it in nothing happenes, no connection, have tried 2 different ones. 5th generation

 

what kind are you using?

 

You’re starting the car either right before or right after the tool is connected, right?

 

I guess thats another question... do I look for codes when the engine is running or the key is just on, new at this.
It seemed to work just fine on my GMC pickup just starting the truck going for a ride and then turning it off .
then I turned the key to the on postion after pluging the reader into the socket, the codes came up.

 

I take a reading with the key in the on position but I do not have to start the car.

If you tried 2 readers that worked fine in your truck but nothing happens in your Maxima, I suspect a bad plug. I had issues before where older ODB readers don’t work in newer cars. I typically get an error. But that does not seem like your issue.

If the OBD reader does not come on at all when you plug it in, there is no power going to them. Try wiggling the reader plug to see if you can get a connection. If that does not work, then look at the plug in your car. Anything bent? If everything looks normal, then your next step is to test the plug in your car using a multimeter to see if there is power coming through.