Took my 05 Forester to the dealership when the engine lite came on. Code was PO131 "02 Sensor low voltage bank 1 sensor 1". The 02 sensor was replaced. Three months later the engine light came on again. Took it to the local garage (dealership is 1 & 3/4 hrs away). After pulling codes "PO131/POO31 - heated 02 sensor open circut-bank 1 sensor 1", they said the sensor needed to be replaced. I just can't believe I have to pay $400 again to have the same thing replaced so soon. Any insight you can give me is most appreciated. Thanks!