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Check engine light is on

2K views 30 replies 8 participants last post by  1996mustang 
#1 ·
Changed to a h-pipe and put mil eliminator on and I'm still getting the check engine light on after the light was shut off, need help to figure out what to do next
 
#7 ·
Got check engine light checked, and code shows p0156 to rich or to lean, eliminated my cats and the check engine light came on, put on mil eliminators that I got from someone last week and light went out for one day and came back on, could the mils be bad or could my rear 02 sensors be bad.
 
#8 ·
Most likely its bad 02 sensor. I had a p0158 for 2 weeks every time I would shut it off it would come back on turned out bad 02 It came on right after I did a tune up so I thought it had something to do with that turned out just coincedence it could just b coincedence that it happened after the mil Eliminators. What I did was swapped the wires on the 02 sensors so bank 1 is reading the bank 2 sensor and bank 2 sensor is reading the bank 1 sensor if the code changes to the oppossite bank u found your problem its more then likely the 02 sensor. That's how I narrowed it down. But while I was down there I just replaced both it was worth it at only 48 bucks a piece.
 
#15 ·
Passenger side rear o2 sensor near stock h pipe.

---------- Post added at 04:41 PM ---------- Previous post was at 04:40 PM ----------

Take a wire wheel or wire brush clean off the carbon put back in reset cel by disconnecting battery for 15-20min then start up see if it comes back before buyi a new one
 
#19 ·
pretty sure bank #2 is on the driver side, since cylinder one is on the passenger side the passenger side would be bank #1, just imo i could be wrong and i dont mind being corrected.
 
#31 ·
The rear o2 will go bad since the catalyst thats supposed to do its job isnt there to do it. With mil eliminators its supposed to tell the pcm that the emissions are good coming out. The only impirtant ones o2 sensor wise are the first ones the upstream since they read the engines performance and conditions.
 
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