Some places to find troubleshooting information for the Volkswagen Jetta include the car's page on RepairPal and Carcomplaints.com. Both sites list common problems for the Jetta, enabling car owners and home mechanics to get an idea of what may be wrong.
Carcomplaints.com lists problems by model year, from 2016 back to 1985. As of 2016, the 2006 model year has by far the most complaints with 128. The top problem for this year is a short in the wiring harness in the driver's door. The year with the second-most complaints is 2002. The top reported issue on RepairPal is shifting problems in high mileage Jettas with automatic transmissions.