I tried to avoid buying the Denso OEM too save some money. What a mistake !!!
Gas milage went down 25% would get misfire codes. Put my old Denso back in and no problems. An engineer told me that the aftermarket Ox Sensors usually are too slow to keep the computer updated in real time. Save the headache and use factory parts for oxygen sensors.

My van is Sienna 2006. The error code was P0158 (bank 2 sensor 2 oxygen sensor). Location of the sensor is at the bottom of engine right under hood lock. The upstream sensor is on the upper front part of the engine, close to the hood lock. Bank 2 sensor 1 downstream sensor is just under the body of passenger seat with connector under the seat. To loose sensors, you need warm up engine for 3 to 5 minutes. When it is clod, it is impossible to remove it. When it is hot, it is very easy. Toyota sensor is type B in Bosch's document. The wiring mapping order is two blacks, one white, and one blue of Toyota sensor for two whites, one gray, and one black of Bosch respectively. Wiring may take a half hour or longer because you want to do it right at the first time. For 15 days and 1400 miles after the repair, no more check engine lights. The problem is fixed. Toyota sensor may be Denson OEM part and costs over $200. The labor costs $100+. It took me one hour and $50+ bucks.

The sensor worked wonderfully and wasn't very hard to put together. I would say that is does require some understanding of what your doing though.
If you think you can handle the assembly, its 100% worth the money you save over buying an OEM sensor

This universal O2 sensor worked perfectly on my 2002 VW Passat. And I saved about 50% over the cost of an OEM replacement.

I had the code scanned on my 2003 corolla by autozone. It said I had a bad catalytic converter. My mechanic said it could be the sensor behind the cat. A new catalytic converter was 979 dollars. My mechanic wanted 235 dollars to do the sensor so I took a chance and did it my self. My check engine light was on for 5 months till I changed the sensor. I disconnected the battery to reset the light. I have driven 1100 miles since then with no light. Changing the sensor was a piece of cake. The old sensor came out easily enough with a wrench. Installed the new one and connected the wires. Done in about 4o minutes. The sensor came with a chart to tell you what coor wire to connect to which. No problems.