1998 4Runner Oxygen Sensor Question

My check engine light came on yesterday. I went to a local mechanic who I use and he plugged into the computer. He read a code PO133, "Bank 1, Sensor 1". My question is how do I know if this is a regular oxygen sensor or a fuel ratio sensor? I want to order online and change myself. Big price difference between the two. I was told Denso is the way to go. Thanks.

As a general rule, trucks manufactured for sale in California have A/F ratio sensors. Others have HO2 sensors. To make sure you get the correct part, give a Toyota parts department your VIN and get the part number from them. You can buy them anywhere as long as you get the correct part number from Toyota.