2002 Kia Sedona XL suddenly downshifts

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For the record: if the sensors they're referring to are the input or output shaft speed sensors, they are very easy to find...just remove the air intake box (where the air filter is) and they're right there on top of the transmission. Input sensor is the one closer to the front of the vehicle, output towards the rear.

Both sensors, input and output are under the air cleaner box. Remove the box, ( black box that hold the air cleaner). three or 4 bolts hold it down, 13 mm maybe. Once removed you will see the transmission. The INPUT speed sensor is under the bracket that holds the shift linkage cable down. Remove the two bolts that hold it down and pull it as you rotate the braket towards the drivers side fender, you only need to move it a couple you will see it there, it's very small with a one plug wire attached. This connector is usually siliconed together, you'll probably break it taking it apart, but only one small bolt holds down the sensor. Remove the bolt and pull it out. Be carefull, there will be allot of dirt and debris built up around it, I would clean the area before removing, you don't want sand and old oil residue falling into the trans. The output speed sensor is about a foot away, towards the fire wall, in the middle back part of the trans. it's very accesible from the top with a 10mm socket and a long extension, use two together to get the length, longer the better. Again one small bolt, sensor pulls out, but remember, the sensors connectors will probably be siliconed together, you will probably break the connectors in a fit of rage. These parts are very cheap plastic and if the car is old 2002-2005, they will be very dry and brittle, have electrical tape at the ready to hold the connections together !! Hope this helps.