How to check if computer is bad.

you have a temp sensor that is giving errant info...think on this car it is more than a coolant sensor, it must measure air temperature too...this device an ambient air sensor should be replaced...how you check is with the OBD-II connector located three feet from your ignition switch...any autoparts store will read your codes for you or your could buy your own scanner for around twenty bucks~

kind of leaning towards a vacuum leak...may not be your ambient sensor...really need the diagnostics please~

I took it in and had it scanned, but it is not giving any codes so the scanner couldn't find anything.

you could start searching for a vacuum leak...one way is to use an unlit propane torch...hold it above the suspected leak and note the increase in rpms~ computers don't go bad...grounding and voltage to them goes bad~

the grounding to your ECM is tenuous at best...as they saw fit to put the 300 amp requirement on the same bus as the delicate 750 Ma requirement...very bad...electronics are delicate...starters are power hogs....a "fuzzy" ground connection translates to varying voltages and varying amperages (fuzzy power) which creates failure conditions....fortunately a SOLID connection to ground with a NEW battery will make it all better~ (should, in my experience)