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check engine/o2 sensor codes

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Old Aug 12, 2006 | 09:00 AM
  #1  
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Cool check engine/o2 sensor codes

i have a '96 f150 with a 351w. i keep getting the 'check engine light' for o2 sensors. they have all been replaced(twice now). i can get the code to clear until i shut it off and then when i start it back up the damn light comes back. any ideas would help. thanks.
 
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Old Aug 12, 2006 | 09:22 PM
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what is the code? O2 sensor code does not necessarily mean the sensors are bad. Often codes just indicates where a non-conformance has been detected, not necessarily where the root cause is. Under normal conditions, if the O2 sensors pick up that the engine is running too rich or lean, the computer will try to compensate by changing ignition conditions. If the effort is moot, the sensor will still record the condition and throw the light as a warning of the failed effort, and that there is an out of control event causing rich/lean conditions. If the code says you have a rich or lean condition, and it is not a sensor malfunction, assume you are running abnormally rich or lean and start diagnosing why.
 

Last edited by puck1263; Aug 12, 2006 at 09:31 PM.
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Old Aug 12, 2006 | 10:16 PM
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From: The OC
Did you disconnect the negative battery cables when you changed them? Clear your stored codes by doing that, then see what you come up with.
 
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Old Aug 12, 2006 | 10:16 PM
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From: The OC
Did you disconnect the negative battery cable when you changed them? Clear your stored codes by doing that, then see what you come up with.
 
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Old Aug 13, 2006 | 06:14 AM
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...Welcome sin, to Ford Truck Enthusiasts!

See you on the boards. ….
 
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Old Aug 13, 2006 | 07:28 AM
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i dont know what the exact code said(thats what the mechanic said). this is what i do know. if i take the neg cable off the codes clear. thay stay gone until i turn the truck off and start it back up. then the light reappears. aside from that it seems to have an intermittent rough idle(its not bad but i can notice it) and a noticeable amount of moisture from the tailpipe. also on start up it takes about a sec too long to fire for my liking. i just bought the truck from a local dealer and it came out of southern illinois so i dont know the history. i can tell that it was WELL taken care of and id like to keep it that way. like i mentioned before its a 96 xlt w/ only 70k on it. not a spot of rust(not even in the rear wheel wells or cab corners!) im gonna post some pics soon. my girlfriend doesnt appreciate that but im betting you guys will. thanks for the input puck.
 
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Old Aug 13, 2006 | 11:56 AM
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while i deal with this problem, i need to replace the exhaust. in my reading on this site am i to understand that a cat back system will gain me nothing but a better sound? that dosent seem worth it to me. at the same time i dont know if i want to spend the money for headers, tru duals either. suggestions?
 
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Old Aug 14, 2006 | 02:13 PM
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AlfredB1979
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From: Alvin, Texas.
Originally Posted by sin
i dont know what the exact code said(thats what the mechanic said). this is what i do know. if i take the neg cable off the codes clear. thay stay gone until i turn the truck off and start it back up. then the light reappears. aside from that it seems to have an intermittent rough idle(its not bad but i can notice it) and a noticeable amount of moisture from the tailpipe.
Well, really, you didn't fix the problem. Hence the returning light. Oxygen sensors are NOT the CAUSE of rough idles. That was just a "feel good" part-swapping mission.

You have to find a better method--yourself, maybe--of checking for codes and diagnosing the problem. That HAD to be a mechanic that didn't care....

Moisture? Byproduct of combustion. No biggie.
 
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