It
sounds so easy--just bring up the trouble codes for your later model
car, buy the part, put it on and off you go!
Except
that it doesn't work that way. Identifying the code is helpful, but
it's only the first step. What the code really tells you is that the
computer is getting information that is not normal from a specified
area. It might actually be a major component, but it might be
something as simple--and sometimes as hard to find--as a loose wire
or a corroded connection or ground. It might be something else that
is not triggering the target gizmo. Could be a vacuum line, or a
crack in a hose. It could be a water or oil or fuel leak that is
seeping onto somewhere other than where the leak actually is. It
could be a loose bolt that is allowing something to be out of its
proper place or alignment. It could be a bad fuse, or a bad
connection in the underside of the fuse box. If a fuse is blown, that
just pushes the question back to the components connected to that
circuit. In other words, you're not dealing with a single
cause--you're dealing with a whole system, with a varying number of
places where something could be messing with the information that the
computer is getting. And some cars are known for having failures in
the sensors and monitoring system itself.
Many
of the same problems are possible in a pre-computerized vehicle; but
instead of a code to chase you are working with what appears to be a
failed component. The approach is the same: before dismantling
anything, check for things that are probably beyond their useful
life. When you do find an obvious or suspicious defect, remember that
there can always be more. Over the years, I have had techs tell me
that "It's got to be this" , or "I've already done
this, so it's gotta be that." My answer is always "There
can always be something else wrong; it is possible to have measles
and chicken pox at the same time." We just finished a job that
came in with everything pointing to the carburetor. Turned out that
the carb was fine, but everything that connected to the carb had
something wrong—clogged vacuum lines, contamination in the fuel,
bad wiring on gizmos that work off the carb. Poor carb didn't have a
chance.
Familiarity
helps, as well. There's always a first time we see a particular
failure, but the more familiar we are with a specific car or system,
the better chance that we've already been there, done that, learned
something. There are some things a technician can figure out the
first time, but there are other things that have odd things going on
that the technical info available may give you a valuable shortcut
to; or there may be things in a particular car that may be a fairly
uncommon add-on that is not mentioned anywhere. We found something
like that just a few days ago. The factory recommended procedure
called for loosening a couple of mounting bolts in the suspension to
provide clearance for the item being replaced; one of the bolts was
easy, the other one turned out to be underneath a part that is part
of a a rare, optional system that had to be partially dismantled to
get to the bolt in question.
There isn't a computer yet that can match the one between an experienced tech's brain and fingers!
