I have received an error code from my Jetta 2002:
16525 - P0141 - O2 Sensor Heater Circ.,Bank1-Sensor2 Malfunction
Would anyone suggest, how serious is the problem? Does it have to be fixed asap or it can wait a few weeks?
The first O2 sensor is the one that the ECU uses to set the fuel-air mixture. If you had a problem with your first O2 sensor, the car would not run at its best.
This error is on the second O2 sensor, sometimes called the "tattletail" sensor. On your Jetta, the second sensor is basically responsible only for turning on the "check engine" light if the catalytic converter isn't doing a good job of scrubbing your exhaust gasses. In other words, it's just checking on the effectiveness of your emissions controls.
If you haven't already gotten a check engine light, you may soon get one. The car will run fine with this condition, but you won't pass an inspection if the check engine light is on. Otherwise, no problem waiting a few weeks to replace the O2 sensor.