On Sat, 3 Apr 2021 19:02:02 +1100, Xeno posted for all of us to digest...

>
> On 3/4/21 5:19 pm, Steve W. wrote:
> > micky wrote:
> >> Are my business assumptions correct?
> >> I'm trying to get rid of some engine trouble codes, and I need to
> >> install 2 or 4 oxygen sensors.** I know I can install one of them, and
> >> if I find a place where I can jack up the car and work underneath, I can
> >> probably do the remaining 2 or 3. I'd prefer to do it myself mostly for
> >> the satisfaction and bragging rights, but also to save money.
> >>
> >> However if I fail with 2 or 3 of them, I would take them to a shop to be
> >> installed.
> >> For no special reason except that I think I know how the world works,
> >> I've always felt that if I buy parts and bring them to a shop to be
> >> installed, the owner will make up the loss in profits on selling the
> >> parts with an increased charge for labor, or something, on the theory
> >> that the job takes the same amount of time minus 10 minutes to order the
> >> parts, and he shouldn't be deprived of the normal income.
> >> Is this true?
> >> Is there a difference if the shop's owner has a reputation for being
> >> honest?
> >> Or do honest shops just charge the flat rate for the job and skip the
> >> profit they would have made on the parts?
> >> If I were in their shoes and I felt obliged to do that, I would be irked
> >> by a customer like I might turn out to be, and I might even, I would be
> >> tempted to rush the job, potentially making a mistake.* Or to skip
> >> almost optional things like cleaning up great afterwards, or putting the
> >> paper floor mat in front of the driver's seat.
> >
> >
> > Well you can **** money away by changing the sensors but it's not going
> > to clear those codes. You have a different problem.
> >
> > As to what the shop does, it depends on the shop. In mine if a customer
> > brings their own parts, they are installed with no testing or warranty
> > given because those are the parts YOU want installed. It is also noted
> > on the paperwork that "Customer supplied parts installed per their
> > direction" That way if the parts are wrong or don't fix the issue it's
> > not my problem.
> > No difference in the labor rate.
> >
> > Now a good shop would bring in the car, do an actual diagnostic on it,
> > then repair the real issue, which in this case could be nothing more
> > than a broken vacuum fitting or bad intake boot that is letting excess
> > air in past the MAF. Or a skewed MAF that is reading a low GPS number
> > and the PCM thinks it's getting less air than it really is. Fuel trims
> > and O2 live data would show that and changing the sensors will do nothing.
> > Also you may wish to know that the only sensors involved with those
> > codes are the two upstream sensors, the downstream units are for testing
> > the cat efficiency and as back-ups to the upstreams if they fail.
> >
> It always amazes me how people think that a *code reader* is the be all
> and end all of engine diagnostics. They seem to think an understanding
> of what's going on under the hood is no longer necessary. Unfortunately
> the diagnostician needs a very good understanding of system operation
> else they will be continually replacing bits which are showing
> *symptoms* of the real fault. This current case is the perfect example
> of a little knowledge being a dangerous thing.

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--
Tekkie