My code reader says P0031 and my CEL, VSC and TC lights are on. I have reset it several times and checked the gas cap. I would assume the P0031 to be the Bank 1 (in front of CAT) sensor. I just replaced this about a year ago. So, do I just replaced both front ones at the same time or just pick one and see if it clears the codes? From the search function on here it seems people often replaced both. Any other things to check other than the 02 with a P0031 code? We are leaving on a trip in a couple of days and I don't think I have time to get a Toyota factory replacement in time. Will a Bosch from the auto parts be fine if I can't get a factory part in time? I'm going to do the change out myself since it's normally pretty easy with the 02 sensor removal tool. It will be going on a 2004 GX470. Thanks!