Two problems related to o2 sensor have been reported for the 1999 Volkswagen Jetta. The most recently reported issues are listed below.
Vehicle experienced several recalls/ and several problems: dome light, vanity mirrors, emissions problems, etc. . . The consumer experienced the following problems with: the interior dome lights, interior trim had come loose on the passenger side, the passenger vanity mirror light did not shut off, the cup holder was jammed and had broken, the driver window sounded as if air was coming in the vehicle, the glove compartment hinges had broken, the air bag light would come on when the radio was turned off, the sensors never seemed to work, the oil dipstick had given abnormal readings(showing low when oil was just changed), the lean oxygen sensor was replaced, the check engine light was intermittent but stayed on, and the catalytic converter was replaced due to noise which ended after the repair(the check engine light had come back on).
My check-engine light has come on three times since late November. The first time it was a cracked vacuum hose. The second time (within two weeks of fixing the first problem) it was the mass air meter. The third time, it came on 5 hours after I was rear-ended January 6th but the dealer said it was not related to the accident. They said it was the oxygen sensor. The serviceman I spoke with at the dealership said he has noticed that this model seems sensitive, causing the check-engine light to come on so frequently. I'm frustrated that none of this is under warranty and with the frequency of these occurrences.