Rear o2 Questions

1QWK96GT

Member
Nov 28, 2004
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Well I recently decided I was tired of staring at my MIL so I decided to make my own mil eliminators. My car is a 96 Mustang GT with mac long tubes, mac offroad shorty h pipe and a flowmaster catback. I wired it all up according to what the schrematic called for, hooked it up monitored the rear o2's and I was only seeing .01/.02 volts max on both rear o2's. So I decided to check my heater circuits and they are working fine since they are wired into the pcm relay and otherwise the vehicle would not even run. Anyway I let the vehicle run until it was in closed loop and the rear o2s are not switching with my homemade mil eliminators. Then I came to the conclusion that I had 2 bad o2's I tried 12 different o2's and they all read .01/.02 volts and dont switch. I am trying to hook up my homemade mil eliminators and monitor the rear o2's and verify that the rears are performing the way they should and wont throw another code. Thanks
 
Rear O2s shouldn't switch. If they do it's an indication the cats aren't working properly. In fact the MIL eliminator is a low-pass filter that is supposed to smooth out the transitions the rear O2 will show with no cats present.

If you're showing only 10- or 20-mV you might have a fault in the wiring. How did you measure the output? Do you have access to a scanner that can show you the rear O2 voltages as seen by the PCM?
 
ohh yeah I mean the fronts are switching and the rears should be about .5 volt I am only seing .01/.02 volts. I work at a ford dealership and I used the IDS to monitor the PIDS.