If it is flashing, there certainly is an issue with the PATS circuit. Have you done the basics such as trying a different key? Also, if the system wasn't worked on, the key wouldn't need to be reprogrammed.
You asked about codes. Yes, there are specific ones that will be set. If you take a look at the pic below, it shows examples of what you may find. See pic 1.
To retrieve the codes, you really should perform a scan of the can-bus. CAN stands for controller area network. Basically, the different computers/modules are tied together via a few wires. This type of scan will retrieve codes regardless of the module storing them. If there are P codes stored, a basic scan tool can retrieve them. However, this may have B codes that require what I mentioned.
Here is a link that explains how it's done:
Let me know.
See pic below.
Tuesday, September 20th, 2022 AT 7:57 PM