“I pushed the button and he looked away”
That parts store person doesn’t have much understanding of this system.
It’s OK to erase the codes.
The car’s computer will simply start testing things next time you drive and set the error codes again when it finds something wrong.
It only takes 30 seconds max to reset the computer by disconnecting the battery.
There are no codes that directly say a particular part is bad.
What were the codes? They look like PXXXX, for example P0123
There could be a bad sensor or a problem with the wiring to it.
It could be a sticky thermostat that’s keeping the engine from fully warming up.