"Dufus Systems" > wrote
> My point was simply that the O2 sensors are the MOST mis-diagnosed
> problems you see today.

I loathe hyperbole--it's dishonest--and doubt we could quantify what system
or part is the most "mis-diagnosed.'

> At 70K miles an O2 sensor's on borrowed time,

I absolutely dispute this. Mine worked fine for over ten years and 150k
miles. 40+ mpg, no problems.

> it's slower than it was new and won't let the ECU control the fuel
> mixture as well as it used to BUT, that doesn't mean it's bad.
>
> Most mechanics either don't bother or don't know how to trouble-shoot an
> O2 sensor code. The code doesn't mean "Bad O2 sensor" it say, the data
> coming from the O2 is out of range so, you need to look in the helms
> manual and follow the procedure.
>
> Say you have a P0131 code (code 1 on older honda's) which is an primary
> O2 sensor code.

I don't think you're exactly wrong in the points you made. For example, if a
car seems to be running fine, and the oxygen sensor code comes up, then I
think this in particular is a situation where you want to see what, besides
a bad O2 sensor, can set off this code. Certainly the codes can mislead the
inexperienced. Manuals are pretty good these days and emphasize that a loose
electrical connection may set off a code and not at all indicate the main
component monitored has failed.

Dunno what exactly you mean by "older hondas," but since there are many
folks with pre OBD-II cars who post here, from my reading an oxygen sensor
not working well will not necessarily set off a code. I think pre-emptive
replacement of oxygen sensors is prudent.

> You go to page 11-67 in the manual, follow the procedure.

That's the factory service manual, which a lot of DIYers do not have.

> Measure the O2 voltage. If it's out of range what's the first thing you
> do? Replace the O2 sensor? No, check the fuel pressure/fuel filter. They
> can cause the sensor to look bad too. There's a whole 'nother procedure
> for testing the fuel system. Its alot easier to just sell you another O2
> sensor and hope that fixes it.

Again, I definitely agree shops will take people for a ride and one must be
careful. I think it's pretty clear that this shop that sold the guy both the
front and rear oxygen sensors took advantage.

But IMO, in other situations, it's not just about 'ease.' It takes time to
do exact diagnoses. That time is expensive.

So I think one shouldn't trust one's shop entirely. OTOH, I think many shops
make choices that are very much prudent when it comes to "replace" as
opposed to "diagnose exactly, repair but don't replace, and risk a comeback
or not truly superior performance."