Recently when I start the engine, sometimes the Acceleration pad is hard to push. Then the battery and add-oil light is on and I can not move the car. I need to shut down the engine and restart it, then everything is fine. This normally happens if I didn't drive the car for a day. In fact, the checking engine light is on for a while with error code 171 "System is too lean on bank 1". The autozone/firestone technicians all told me it is because of oxygen sensor. I don't think the oxygen sensor can also cause start problem. Can anyone give me some suggestion/advice about the possible problem? I am not familiar with cars. Any help will be greatly appreciated. Thanks in advance.