View Full Version : Check engine light came on....

08-02-2007, 07:28 AM
and I took it to a mechanic, he checked obc....said it was running a little rich, but I could feel no difference in driving it. :(
He said it could be the O2 sensors, since I have never changed them out. (56,000 miles on cobra) :dunno:
He cleared it and it has not come back on .
My question is, how many O2's do I have and what do they cost? and does that sound like the problem, or could it be something else?
Thanks for the help :)

08-02-2007, 09:24 AM
You have a total of 4 (2 front, 2 rear) O2 sensors...most likely the one's that threw the CEL were the one's up front...they'll run you about $75/each and you're looking at about an hour for labor at a shop...there's really nothing to changing them, but if you do not have a lift or jack stands, it would be impossible for you to do in your driveway.

08-02-2007, 09:56 AM
Thanks, for the info, I have a friend that can help with this.

08-02-2007, 10:24 AM
Did the mechanic give you the code? Otherwise, yes, the O2's are pretty simple to change out.

08-05-2007, 11:16 AM
There are many things that will affect the performance of the O2 sensors. Carbon, Leaded fuels, silicone lubricants, coolant in exhaust are just to name a few. Life expectancy of O2 sensors is typically 60k miles before they drop in performance (ability to generate voltage from the reaction of the probe materials when present in oxygen). Over time the response becomes slower which will lead to a rich fuel ratio. It is possible to have them last much longer than 60k miles but that is the nominal operating range and beyond that it is just time until the emmissions system begins to run in open loop which would result in an extremely rich A/F. O2 sensors cannot be cleaned by any means due to the nature of the materials, once the reactive plates in the sensor have been compromised there is no way to restore them except replacement. It may take a while before the check engine light comes on. The codes are important since they would indicate the condition of the sensors. If reported as not responding, slow response would indicate replacement or out of bounds voltage on the sensor may indicate some other issue, loose connection or corroded sensor.

08-05-2007, 04:08 PM
Thanks for all the help guys. I took it out for a spin today, and within driving it 15 miles it came back on, :nope: so I guess I will be changing them out.
I am going to get the code tommorrow on it and will let you know what it is. Should I go ahead and replace all 4 or just the front ones? I am guessing the code won't tell me which ones? :doh2:
I found some at O'Rileys (?sp)$65 each, they where Bosh(?sp) I was told not to get the universal type as you have to splice some wires in, I think they said! :thumbdwn:
Are the Bosh alright or do you recomend something else? Sorry for all the question, but I need the help. :scratch:

08-06-2007, 07:10 AM
The original OEM for ford is Bosch. The O2 sensors I pulled from my explorer had the bosch logo on them along with Ford and the associated numbers.

In some cases, they may offer several O2 sensors for your model year. In reality there is no difference between any of the 4 sensors except for wire harness length. Depending on where the connectors are, may be a hard reach.

08-06-2007, 03:02 PM
Well, could not get the check engine light to come on but we check it ...no codes, but some how he did another test on it with same tool, and it said bank 1 & 2 were running rich and the egr was wide open, so he told me it looks like it is the DPFE sensor, he showed me where it was at and the called Ford....cost is $100, does this sound like the problem?
This was a mechanic at work so he is not trying to make money off of me just helping....what do you think?

08-07-2007, 07:23 AM
The EGR will open up when the engine is running rich, however there will be a code if the EGR is flowing when it should not be open. DPFE is just the differential pressure sensor and indicates how much EGR control is needed to cycle the EGR valve. That could be a fault if the DPFE is not operating properly or measureing the exhaust and intake pressures properly. This could also indicate fault with the EGR valve if it is stuck open. Did your mechanic run a diagnostic on the emmissions? That would test the O2 sensors as well as pinpoint the EGR components at fault. Same test used for emmissions testing. I have had so many of those replaced on my 96 explorer usually when I suspected the EGR valve was at fault.

08-07-2007, 07:47 PM
well here goes...long story short, :(
(code was PO172...system to rich bank 1) put the DPFE on yesterday evening, it seemed to run better but still had a slight hick-up in the idle. :scratch: on the way home today check engine light came on again, :mad: stoppped at a mechanic shop, read the code, this time it was PO175....system to rich bank 2.
The mechanic there, a good friend said the EVR needed to be changed when I changed the DPFE. he had the EVR, put it on and said no charge! :thumbsup: (I don't know how much they cost) The idle went back to normal and he said that should fix it.
I will drive it tommorrow and hope the check engine light stays the heck away. :dunno:
I want to thank everone that has help me so far, especially Ausie, hope this is the end of it ! :clapping:

08-08-2007, 07:04 AM
You are not out of the woods yet. You still have that rich condition to contend with. I had this site on my favorites list (has all of the generic ODBII codes and some specific codes for each manufacturer). Check out the link below. As for the issue of running rich, do you still have the factory H pipe or aftermarket with or without cats? If you do have an aftermarket mid pipe without cats you will need to replace the secondary O2 sensors with MIL eliminators (not sure what the error code would be if you did not use the MIL's). Assuming the mid pipes are stock or have cats, (would be nice if the code indicated which O2 sensor detected the rich condition vrs bank 1 or bank 2), there are a few things you can check or have your mechanic check.
Fuel Pressure pressure may be too high or injector flow too much. Dirty MAF sensor or sensor out of calibration.


The hick-up or sputtering is due to a miss-fire of one or more sparkplugs. Either the gap is too large or plugs are due for replacement but this will also happen if running too rich. I would check the air filter and replace if necessary. Another trick is to dump the EPROM memory to ensure that the PCM is not operating on old data that is stored in the EPROM. This will allow for the PCM to rebuild load tables and corrections on the current operating conditioins. Clearing the codes will not erase the EPROM memory, it would be nice if it did but that does not happen. There are two ways to dump the EPROM memory, If there is a fuse for the PCM memory or EPROM memory just pull the fuse for about 1/2 hour, the tried but true method is to disconnect the negative terminal of the battery for the same amount of time (better this way than the fuse method in case you forget to reinstall the fuse). Talk to your mechanic about this.... see what his thoughts are. Also, if there are any issues that are hidden due to old data, they will surface as the PCM relearns (rebuilds load tables, ignition timming curves and A/F corrections). Best to do this after the following: replacing air filter if it is shot and or sparkplugs. If you have ever looked through any guides, the typical first step is to disconnect the battery (obvious is to prevent any short circtuits that could possibly occur when servicing some of the electrical components, the hidden feature is that it forces the PCM to relearn since it only stores data up to a certain point). Note, dumping the EPROM is not a garantee that the codes will not re-appear. Sometimes it can help discover issues that were ignored since some of the ODBII error codes have priority over others that hava a low priority which may have been the root cause for the priority code. I am still learning how this PCM system works, so do not take my suggestions as absolute, sometimes I may be dead on or way off. What makes it worse, I am an Engineer, not a mechanic.... enough said.... :thumbsup:

08-08-2007, 07:23 AM
well your right, I am not out of the woods, the CEL came back on this morning,
I still have the stock cats and no h-pipe or x-pipe.

A code P0172 may mean that one or more of the following has happened:
A code P0175 may mean that one or more of the following has happened:
"The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters (K&N, etc.) can cause the MAF to become dirty if the filter is over-oiled "

I read this and thought....just before this check engine thing started, I had the oil changed and the K&N filter recharged. (they did the charging) Could he have put to much oil back on the K&N?

I am goint to read codes again this morning and see what it says this time, and let you know

08-08-2007, 09:48 AM
Yes! This has been discussed over on Mach1registry.

How much oil is to much on a reusable filter?


08-08-2007, 10:45 PM
Here is a word of advice to you and anyone else reading this thread.

It is not worth the time or energy to "recharge" your K and N filter as all of the originals are done by machine and the proper amount of oil is applied every time. Numerous people over oil the filter and as a result have problems. Break down and spend the few extra bucks to insure proper amount of oil on your filter.

08-09-2007, 06:50 AM
I would agree with Cobrabitn you would be better off replacing the filter with a new one. Not only would it affect the MAF sensor, the oils may indeed cause other issues depending on its composition (especially if it is a silicone based oil which not good to O2 sensors, once it burns off in the combustion chamber, silicon fumes will react with the O2 sesnor elements as well as the CATS and cause issues). I used to have similar problem when I replaced the paper filter on my Explorer, check engine light would always come on indicating O2 sensor fault shortly thereafter. At that time, I used the paper variety. It is not required that the manufacturer list or state the type of oil used on the medium (paper or cotton gauze). The high flow filters are good for a few years then toss them out for new (all depends on environmental driving conditions).

It could be as easy as a contaminated MAF sensor and using the proper chemicals will correct the issue (CDC electrical parts cleaner or Berryman's B-12 chemtool will not leave behind any oil residue, I have used both without any problems). I have yet to use the K&N filter in any of my Cobra's due to the loose fit on the 01 (I bought one but returned it since the sealing lip was too small to fit the factory air box). With the 04, it requires a slightly larger filter due to the extension in the throat of the MAF housing. Best filter I have had so far was the GREEN filter.

08-09-2007, 07:28 AM
Well took a half a day off yesterday went to a friends business, which happens tp be an Amsoil dealer. :)
Was going to just get one of his filters. Well we set in and for approx. 3 hours we took everything apart from the filter to the S/C on up to the intake...... it was saturated with oil, :eek: (the spray can of oil that was in the recharge kit, he had emptied it onto the K&N filter, it was dripping and so was everything else) :eek: :mad:
We wiped them down, sprayed them the electrical cleaner let them dry out and then put it all back together. Drove it this morning so far, so good but I was told it may still set some codes off until we get it all out of the system..... :mad:
I am also going to put some fuel injector cleaner in my gas to maybe help that out. :)
This has been a learning experience for me cause I usually recharge my K&N myself, but got lazy this time and let someone else do it. :mad:
Thanks again for all the advice and help. We will see what happens next
"As the World Turns" ...like a soap opera :eek:

08-10-2007, 06:30 AM
IF the saturated intake tract was coated with red sticky stuff, that would be the filter charge oil. However, if you had found pools of it in the intake that could indicate another issue other than a saturated filter. Hopefully the problem is not a bad bearing seal on the Supercharger similar to what SuperG had......

The MAF sensor is very sensitive. My thoughts on that would be that it would run lean if anything else since the amount of air would be masked by the contamination on the sensor. Not exactly sure what response the O2 sensors would provide if you were burning oil, assuming the bearing seal of the supercharger is at fault. It could be from the tune itself if set too rich to begin with....... There are several sources for oil that you may have stumbled on in the intake tract...... Brealther line (if still connected), PCV line but this souce is direct into the intake plenum, and the last would be the from the Supercharger itself if the seals are blown (leaking oil, either the SC is self contained or supplied by the engine). If the engine is burning an excess of oil (not the typical left behind film from the rings), that would definately create a problem, clogged cats as well as slow response on the O2's. The O2's can be tested with some scan tools by performing an Emissions test, unless the ODBII codes are inhibiting the test (which they will).

08-10-2007, 07:29 AM
Actually from the S/C to the intake was pretty dry. :) From the K&N filter to the S/C was the part that was saturated. :(
The S/C sounds normal, if that can be, :D but again I am no expert.
During the clean-up I disconnected the Battery hit the brake, (I was told that would clear everthing).
Then when we were finished, started it up, let it idle for 20-30min. then turn A/C on for ten then drive it.
I drove it Wed. evening, Thur. morning, at lunch and evening. And this morning. and so far no CEL :D
But that not to says it won't .
but I did not see much of anything from the S/C to the intake, but did not see into the intake. :dunno:

An emmision test was performed and the 02 sensors were reading correctly. The tool he had showed just about everything and what it was reading or doing. So bottom line I not sure whats happening, but its running and no CEL, crossing fingers :eek:

08-10-2007, 09:14 PM
Glad you got it running right...I still stick with my advice in post #14. :)

08-11-2007, 09:06 AM
:thumbsup: Hopefully you replaced the filter, and cleaned the MAF.

08-11-2007, 01:41 PM
yes, we did clean the MAF, but could not replace filter yet, but did clean it real good and ordered a new one from Amsoil. :thumbsup: It will be here Monday.
The CEL did com back on friday and the code was P0131, :( the bank 1 sensor 1.... 02 sensor, but I am goin to run it for a while and check it each time the CEL comes on and see if it will eventually clean out. If not I will just change it. That is the only code it is throwing now so hopefully it will clean up :)
Thanks for your help it has been greatly appreciated. :thumbsup:

08-15-2007, 03:20 PM
going to put the new filter on today, the CEL has not come on all week, so I hope that did it,
I just want to say thanks again for all the help on this, expecially to ausie :thumbsup:

08-16-2007, 07:42 AM
Considering what has been happening, it would not hurt to have your tuner take a look into the rich A/F condition. Sometimes it is just the simple things that creates a problem that seems major but could result in major repair if left unchecked. I would make that a definate plan if the check engine light comes back on or if you detect any pending codes. Sometimes it is a good thing to have your own OBDII scanner that can read all the standard ODBII codes along with the specific FORD codes (if that is at all possible). I would still check for codes periodically just in case.

08-16-2007, 11:32 AM
I did buy me an OBDII scanner from mac tools, its small and compact and will read codes, tell you what they are, clear them, etc. :) Comes with a CD and a book on all the basic codes and ford specfic. :)
Problem is, my tuner is over 100 miles away, but still it might be worth the trip. :)