I have a 2004 mustang gt with offroad x pipe and mil eliminators. Getting code P0420 every few days after clearing the code . So I swapped the rear sensors from left to right to see, if it was a bad sensor if it would change banks. Well it just came back on and I still have a P0420 for bank 1. My question is when I put my x pipe on the bank 1 upstream sensors threads got ruined. So the front sensor is brand new and the other 3 have 65k on them , do you think the reading between the new front one and old rear one could cause an issue ?? Cause it's pulling the same code with the rear 02's swapped or not. And just FYI it has had this set up for around a year with no troubles till now.

 

bad MIL's.

 

I had 1 bad MIL when I first did the set up and I got a p2270 bank 1 sensor 2 stuck lean. I ended up doing a homemade MIL for that side and like I said haven't had any problems since. I just assumed if my other MIL went bad I would get the same P2270 code. But now it's a p0420. Just so no confusion , the MIL that was bad was on the passenger side. When I did the home made MIL I put it on drivers side. So the MIL on the passenger side is the original. I'll test voltage on monday and see.

 

Here's how to make your own...

 

Thank cliffyk thats the "how to" I used to make the one for the drivers side and it worked like a charm. I just cant data log or test the 02 sensor to see if it's bad.The dealer I work for is Toyota only laptops. I can monitor under generic obd 2 and see the voltage etc... but not much else. So I deceided to swap the rears to see if I would get a p0430 instead of a p0420. Then I would know the sensor was bad, but that didn't happen . So more than likely another faulty MIL.