Q: Jetta not shifting when cold

If your vehicle is not shifting from 1st to second that may be indicative of a few different problems. I would suggest having the vehicle’s shifting issue inspected by a knowledgable technician, such as one from YourMechanic, as the nature of these types of problems can vary greatly. I would first check to see if any trouble codes are present that could perhaps give us a clue to the solution. This transmission has an electronic solenoid that shifts it from first to second, and it will not shift properly if this solenoid has failed. If the solenoid checks out, I would move on to the transmission itself. Sometimes shifting problems are due to contaminated or dirty fluid, so a fluid change may be required. This particular vehicle, however, uses a sealed transmission that requires a total flush and fill, using the correct fluid. If both of these check out, I would suspect the transmission itself may have a mechanical or internal pressure sealing problem, and may need to be overhauled.