Check engine light came on, so I had a diagnostic test done at autozone and the code P0015 came up. what's this about and what should i do?

This can sometimes happen depending on the type of smog test being done.
The best thing to do is take your car to a local shop or Autozone (autozone will do this for free) and have them pull the trouble codes and reset your light.
There might be a problem that is on the verge of occurring that the smog test helped reveal.

When the check engine light is on eco (economy) is disabled. You now need to have the OBD2 fault codes read, this is done at the diagnostic port under the dash on drivers side with a OBD2 scanner or code reader. Also Autozone parts stores will do the test for free.

You have a car that is fully electronically controlled and is able to self diagnose this type of fault, what needs to be done is to have the engine control computer scanned for fault codes, once you have the fault code(s) you can start the diagnostics to repair the problem. This test is referred to as a OBD2 fault code test, any chain auto parts store like Autozone can do the fault code(s) test free.

Ask for a OBD2 fault code test

Check engine lights are to be reset using an ODB II reader. You can usually have this done for free, both reading and resetting the code, at any Autozone. If Autozone is not nearby, try any parts store that DOES NOT offer mechanical services. Stores with mechanics will want to charge a diagnostic fee. Stores that only sell parts will do the reading and resetting as a free service to get your parts business. Also, knowing the code may make it easier to fix permanently as the lights usually come back on after being reset unless something was actually done to correct the problem.

If you have a service engine warning light showing up on your instrument cluster go to Autozone and get a free diagnostic test done. They will give you the codes and explanation.

Hi.

If the check engine light is on there are codes stored on the ECU (the car's main control module). Do a DTC scanning (diagnostic trouble codes scan) using an OBDII reader. In US the scan can be done for free at the nearest Autozone. The resulting fault codes will tell us about the nature of the problem.

take your vehicle to your locale autozone, they do free diagnostics tests. They'll tell you what codes your vehicle is sending out(Plus alot of information about that code, what needs replacing)
Good luck

Any thing could be wrong. The best thing to do is to take it to Autozone or to a shop and have diagnostic test done on the car. Autozone does not charge to have it done and most shops will not charge you if they do the work.

Take it to Autozone and get an engine diagnostics done. They have a scanner that will give you the code that is causing your check engine light to come on. you can troubleshoot from there.

take it to autozone or advanced and get a free check engine diagnostic test done, they will tell you what it is