I've got a 2009 Aveo LT, with an OBD code P0599. I hope someone out there knows what it means, because I haven't been able to find anything.

this link should help Service Manual2008 Aveo Diagnostic Trouble Code DTC U0001

P020 has to do with the cam shaft position sensor

Thread Recall notice for 2009 Aveo

was your vehicle on the recall list? call a local dealership to find out if you need the newer part # and the gap is listed on post #1

eventhough it's for a 2009 model, owners of this vehicle from later years are replying there and having their spark plugs replaced FOR FREE

plugs are the last point for engine missing.
check fuel pressure , injector/s HT leads , cracked distributor cap, moisture on coil/s, vacuum leaks,.
run the fault codes

ful pressure cat converter and many more

the code means this ECM/PCM INTERNAL ENGINE OFF TIME PERFORMANCE

The unique way to know what means this warning is scanning the PCM (Powertrain Control Module); visit Autozone or AutoShop with OBD scanner reader and note this fault code.

With this code number could send additional details to diagnostic and solve it. Keep in touch.

you can take it to anyone who can read the OBD codes, check around , Lots of places still read the codes for free,, Once you get the codes Post them here, someone will assist you in what the codes mean, and possible fixes for the code , if you reply to this answer I'll help you ,, It could be anything from a O2 sensor to a dirty throttle body and everything in between,, so get the codes read, But to answer your question, dealers tend to be expensive, but they honor their work,, but any shop should be able to help you , as long as your comfy with them and trust their work

OBD-II Diagnostic Trouble Codes (DTC)

DTC Codes - P0500-P0599 - Vehicle Speed Controls and Idle Control System

P0562 System Voltage Low

Hope this helps.

P2135 Throttle Position Sensor (TPS) Property Malfunction, remember this is not a car that is built by GM it is a Korean import.