o2 sensor problem

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04-09-2008, 01:48 PM

mustang_montana

4th Gear Member

Thread Starter

Join Date: Feb 2005

Location:

Posts: 1,907

o2 sensor problem

i have brand new motorcraft o2 sensors upfront, the wiring harness and pcm check out fine yet the sensors arent working right. again the wiring is 100% fine. however, my rear o2 sensors are disconnected (they are turned off in my tune ) would this be causing issues with the front not having the rear connectors connected to anything? i cant connect them to anything right now as the rear o2s were just generic ones i used to plug the holes, but i have some spare ones to try out, just curious if this is how the circuit works. i checked out the diagram but it didnt tell me much along those lines. thanks a lot guys. get ready for some before and after pics for those who remember my car, lots of changes

04-09-2008, 02:22 PM

98SN95

2nd Gear Member

Join Date: Nov 2007

Location: New Orleans, LA

Posts: 362

RE: o2 sensor problem

did this just happen or has it been this way since the tune?- does the rear o2s connectors still have 5volts at the plug?-

04-09-2008, 02:24 PM

Rusmisel01GT

5th Gear Member

Join Date: May 2006

Location:

Posts: 2,111

RE: o2 sensor problem

Well, havent seen you on here in a while, I remember nominating you for ROTM but you were long gone... LOL, anyways.

What do you mean there not working? is the engine light coming on? or what? Its possible you were sold faulty sensors... doubtfull... but possible.

04-09-2008, 02:36 PM

Derf00

Gentleman's Relish

Join Date: Feb 2005

Location: AZ

Posts: 13,090

RE: o2 sensor problem

Quote:

ORIGINAL: mustang_montana

i have brand new motorcraft o2 sensors upfront, the wiring harness and pcm check out fine yet the sensors arent working right. again the wiring is 100% fine. however, my rear o2 sensors are disconnected (they are turned off in my tune ) would this be causing issues with the front not having the rear connectors connected to anything? i cant connect them to anything right now as the rear o2s were just generic ones i used to plug the holes, but i have some spare ones to try out, just curious if this is how the circuit works. i checked out the diagram but it didnt tell me much along those lines. thanks a lot guys. get ready for some before and after pics for those who remember my car, lots of changes

There is a feedback loop that must be "seen" by the computer or you will have the check engine light on. Regardless of whether or not you actually use the rear O2 sensors. To simply have the harnesses unplugged will give you problems. You either need 02 deletes (caps that plug into the factory 02 sensor and fool the computer into thinking the O2 sensors are tehre) or leave the o2 sensors plugged in but turn off the reading (as you have) in the tune.