I have 97 ford expedition 5.4 which check engine light is on. Had the code scanned, and it is P0171, cleaned MAF Sensor, next step is O2 sensor. I have found all 4 sensors, but we are thinking the sensor that is out is the front sensor on passengers side. I have found the sensor, but it is up in the fender for the most part, getting to the sensor it self isn't a problem, but getting it unplugged is. Any suggestion from anyone they may have changed this one, I would really appreciate it.

 

I believe they make a special wrench for removing 02 sensors, but I'm not sure. I know I saw one somewhere. You can't put a deep socket on it and a ratchet wrench won't slip over the sensor. I used an open ended wrench, but it was a real pain when access is difficult. Another possibility is a curved open ended wrench. In case you don't know, disconnect the wire first so it wont twist as you unscrew the sensor. Good luck.