What's the p12a2 vw code?

Diagnostic trouble code (DTC) P12A2 on Volkswagen vehicles typically means that the fuELRail pressure sensor is giving an inappropriately high reading. This can be caused by a couple of different problems, but they're all able to be traced back to the fuELRail pressure sensor. You'll either have a bad sensor, an open or shorted harness, or an otherwise poor electrical connection. The recommended first course of action is to replace the sensor, though this is often more expensive than replacing the wiring. To potentially save Yourself some money, make sure You thoroughly inspect the wiring -- if You see any areas that look damaged or short circuited, it's a good idea to replace the harness. Otherwise, the replacement of the sensor should take care of Your problems.