I just replaced my transmission in my 2001 Expedition. Only 40 miles of driving and I have a SES light now. The code is PO135 which they tell me is the O2 sensor (Bank 1, Sensor 1). Is it possible that something happened in the installation of my transmission to cause this code? Or is it simply a freakish thing to have an O2 sensor go bad at the same time I had my transmission replaced? I love my new transmission. . flawless shifting and the Expedition runs super nice!!

 

Did you check to make sure the 02 sensor is plugged all the way in.. Or could the harness or connector been damaged during the swap?

 

That's what I was wondering. . It drove fine today. . there is no indication of fuel/mix issues in the idle. Possible that the mechanic could have disconnected it while installing the trans? I'll look for that and report back.