I searched the forum for related threads but for the only question asked, the answer link provided would not open. Please excuse the bandwidth if my question has been asked and answered before.

I have a 2000 4Runner that continues to throw a 0171 check engine code. If I reset it, it will reappear in a few miles of driving. I have replaced the air filter, fuel filter, front O2 sensor and the truck has a recent tuneup. The truck runs very well at all operating temperatures. Any thoughts on what might be the problem? Louis Herndon

I don't remember if it was exactly the same code I had on my 1999 4Runner, but it ended up being the MAF (Mass Air FLow Sensor). Replaced the O2 sensors and Cat. Convertor before I found out it was the MAF sensor.

It is connected to the hose going into the Air Filter housing by a few phillips head screws. Mine was bad (~$150) but Toyota had told me to try cleaning the sensor with a q-tip and some alcohol (be careful not to damage the sensor). Disconnect battery to reset code, and drive it to see if the check engine light comes back......