Where is the engine code located on a 2001 Volkswagen Jetta Wolfsburg edition?
It's stored in the engine control unit (ECU). The ECU is read with a device called a scanner. There is a on board diagnosis (OBD II) port under the dashboard usually around the steering wheel. -- Repair shops and auto parts store will read the computer and tell your what part is failing in an attempt to sell you parts and service. Get the code number, write it down and post it here. We can advise on the best course of action to solve the problem in the most economical fashion.
The ECU stores the codes that turn on the check engine light (CEL). Some scanners can detect some that are called pre-codes. Those are codes that have not happened enough to trip the CEL.