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I have 1999 F250 v10 5 speed manual transmission and my service engine soon light popped on . So I drove to auto zone and they ran a check of the codes . It indicated just one code P1151 which they said was mass air sensor so i bought one installed it and also bought a code scanner . So I drove it for about an hour light pops back on giving me the code P1151 again . I erased the code and this morning after 20 minutes of driving it pops on again. This is getting frustrating . Anyone have any ideas why ? I am almost certain the new sensor is working because truck seems to run ok . Plenty of power and does not appear to be eating fuel . Could simply replacing the air cleaner fix this problem it is due for an air cleaner . I am just not sure where to look now . Any suggestions ?
First of all go back to Auto Zone and smack the guy in the face who told you P1151 was a MAF sensor code. P1151 is lack of HO2S-21 switches - sensor indicates lean. This is the bank 2 (drivers side) Oxygen sensor, where the sensor is not switching from rich to lean like it should. Now before you go out and buy a new O2 sensor, make sure there arn't other things that could be causing this to occure. A lean condition in bank2 can be caused by things like a vacuum leak from the intake manifold or some other unmetered air leak. Make sure you check this out first. However, if your truck has over 100k on it, it is probably just the O2 sensor. They really arn't designed to last much longer.
Last edited by rlh68050; Jun 27, 2005 at 09:36 AM.
Check the PCV valve elbow where it connects to the throttle body. Lots of people have gotten lean (or other) codes from that vacuum leak.
Check everything else for vacuum leaks too...
The MAF usually doesn't go bad, just needs to be cleaned. I've seen cars that do not produce codes where the MAF was so black with gunk it was amazing. After cleaning, they ran much better...
Anyway... check the wiring to that O2 sensor also! But if all else fails, replace that darn thing.
Thank you i will look for vacuum leaks first and if I do not find any I will bite the bullet and replace the O2 sensors . It is my understanding they should be Replaced in Pairs . Hopefully will not be too hard to replace them . I bought my own code scanner for this reason and i just installed software on computer and looked up code and you are right . One would think if they are going to scan codes for free they should give the correct answer.
One would think if they are going to scan codes for free they should give the correct answer.
I work part time for an auto parts store, Murray's Discount Auto, here in MI. They arn't as big as Auto Zone, but still have about 100 stores in MI, OH, IL, and IN. We DO NOT offer this "testing" as a service to our customers for the very reason you described in your post. NONE of our employees (Auto zones either) are qualified to make diagnosis using these scan tools. If it was as easy as plugging the scan tool to the vehicle, reading the code, and replacing the component that the code lists, drivability techs wouldn't be making the money that they do. It takes a very high skill set to understand the complexities of a modern vehicle.
If i should need to replace these o2 sensors are they very difficult to remove afterall they do have 106000 miles on them . I know I will need the o2 sensor socket but will just wrenching them out work or do I need to use a torch to heat them up first or Rust buster ? I never had to replace these on any vehicle I have owned .
I've never done it either, believe it or not, but shouldn't be too hard, the exhaust is stainless steel (mild, but still, stainless steel)...
I would certainly put some penetrating oil on it (NOT wd40!), and try to get as much of it off as possible after getting out the O2 sensor - it'll smell real nice if you don't.
Thanks guys I will investigate this tonite when I get home from work and will repost when i get problem fixed . I looked at wires at lunchtime and they appear to be in good shape . Will listen and look for vacuum leaks again but still came up empty handed . If i cant find any I will just install the 02 sensor on drivers side and see what comes out of it .
Ok guys got It fixed . I searched for vacuum leaks and found none . So I replaced the O2 sensor on the drivers side and erased the codes . I have driven around 100 miles and everything seems fine now . For those of you who have never done an O2 sensor it took around 5 minutes maximum to change . You heav to love stainless steel exhaust . I stopped and bought the sensor and before I left the parts store I squirted the sensor with PB blaster and drove home . The sensor came right out with absolutely no effort whatsoever . I normally dread doing any exhaust work since it aleays ends up a nightmare but with the stainless you are not dealing with a rusty mess . Thanks for the information.
Slightly unrelated, but I drove 60-70 miles after forgetting to hook my MAF back up and didn't get a code. Didn't really notice any difference except rough starts.
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