Check engine light has been on for a long time. 4 diagnostic codes: PO128, PO315, PO604, PO62F I can't find what the codes mean.

Take it to a qualified repair shop , you don't have the diagnostic knowledge or tools to fix this , just because you can read codes doesn't mean you can diagnose an fix it ,

PO128 -- engine coolant low or thermostat not working
P0440 - EVAP system malfunction, gas cap loose - Cat convertors missing from car can cause this
P1189 - Engine Oil Pressure Switch Circuit -- CAT CONVERTORS MISSING FROM CAR can cause this.

Oil pressure switch issue
Coolant temperature sensor issue
EVAP system issue
All different issues, so I suggest seeing a mechanic.

PO 128 is a coolant temperature beyond threshold code. It means your thermostat is stuck and needs to be replaced.

P0128:
P0128 OBD-II Trouble Code
Technical DescriptionCoolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)

What does that mean?This means that the engine's PCM detected that the engine has not reached the required temperature level within a specified amount of time after starting the engine. The intent of the P0128 code is to indicate a faulty thermostat. Similar codes: P0125

In determining the engine did not reach a "normal" temperature, it takes into account the length of time the vehicle has been running, the intake air temperature (IAT) sensor reading, the engine coolant temperature (ECT) sensor reading, and the speed of the vehicle.

CausesA code P0128 may mean that one or more of the following has happened:

Low engine coolant level .
Leaking or stuck open thermostat .
Faulty cooling fan (running too much) .
Faulty coolant temperature (ECT) sensor.
Faulty intake air temperature (IAT) sensor .Here's a link on replacing your thermostat.

it mite be a o2 cencer

no the code PO128 on the cobalt mean defective thermostat. nothing to do with driving experience

miss fire codes need to check tune-up, proper spark at all cylinders

replace the thermostat. computer sees engine is running too cool thermostat stuck open.

this is a coolant below threshhold code meaning engine is running too cool. change your thermostat and will fix problem. if you cant clear code after a few drive cycles the computer will cut light off once it sees problem is corrected