Check Engine light / OBD II codes

[fbarr]

Hi,

I just bought a 2000 Explorer Sport in August and the dealership, which I've been going to for a long time, performed all the repairs that my mechanic said were necessary after his inspection.

However, just after the warranty expires on me, the check engine came on last Friday (12-8). I was hoping it would be something simple, so I checked the oil and antifreeze levels. To my surprise the antifreeze overflow tank was empty, so I filled that about halfway, but the light was still on.

I then learned that Auto Zone offers free OBD II code reading, so I went there on 12-12. The guy there said it came back with codes P0171 and P0174 and told me that these codes meant I needed a new mass air flow sensor, which he quoted a price of $122 plus an $87 core charge for. He also said that not replacing it would reduc gas milage. I asked about clearing the code and I was told that was illegal for them to do.

I then went to a different auto parts store on 12-14 and found out they also offer the code reading after I told the man in this store what Autozone had told me. I asked if the part needed to be totally replaced, or if it was possible to simply clean this part or something of that nature. However, it seems that this man misunderstood what I was asking, because he took a code reader out and CLEARED the code. Thus far, the light has stayed off but he said it could come back on if there was still a problem. I did fill up the gas last night and the milage that I calculated after doing so was the worst result I've yet had since buying the Explorer (13.5 mpg).

I guess my questions are:
1. Since the light hasn't come back on (yet, anyway) could it have been some kind of fluke? Should I leave things alone as long as the light doesn't come back on, despite the low mpg I just got?
2. Does anybody know if the codes Auto Zone gave me do indicate a problem with the mass air flow sensor, and if so, does it need to be replaced completey or can it be cleaned or anything of that nature?
3. How reliable are the codes? Are they subject to misinterpration by the person doing the code scanning?

I would greatly appreciate any ideas or advice that can be offered.

Thanks,
Frank

 

[floydr007]

p0171 and p0174 are extremely common. I'm surprised he didnt try to sell you oxygen sensors. These codes, if you arent already aware, mean that bank 1 and 2 are registering lean. You could start with cleaning the mass airflow sensor (search on how). Theres a very good chance that you have a vacuum leak, however. Search the intake manifold gasket leak on these forums, and youll find thousands of threads. Theres other possibilities, but a vacuum leak is the usual culperate for these codes. My car threw the same codes about a month ago (when it was really cold), and I had the mass airflow sensor cleaned and reset the computer, and it hasnt come back yet. I definitely have a vacuum leak, and will be getting the OOM12 kit installed within the week (you could search on that too lol). Good luck...