Purchased a 2008 Tucson for my daughter last summer. The check engine light came on shortly after and indicated problem with Bank 1 Sensor 1 Oxygen sensor. Replaced at local station with NAPA sensor and problem reappeared within 100 miles. Hyundai said that I must replace with Hyundai sensor due to tight tolerances on this engine. We tried this and the problem was gone for 6 months (the car is not driven very far. only about 2000 miles over this time frame). Now the problem has returned. We just replaced the sensor again. Luckily Hyundai replaced it under warranty from the previous repair. Has anybody had a similar experience and/or reason why this is reoccurring?