On Thu, 31 Jan 2013 18:16:56 -0800, Erik wrote:


And from 1996 on up, diagnostics is a lot less of a "black art".

Not so! Especially with some mfg's.

Here's an excellent example:

http://www.youtube.com/watch?v=3-MTko-otio&feature=em

Yes, I know it's long... runs just over 40 minutes... make some popcorn
& kick back.


Good vid for tech geeks. What, a couple hours reading meters,
flowcharts, schematics, tracing wires, thinking, speculating,
thinking.
All to find an obviously hosed wiring harness that should have been
evident after about 10 minutes of inspection.
That's what I do first with all electrical faults, unless experience
tells me otherwise. Especially if I see a leaky valve cover gasket
has soaked a harness with oil.
BTW, you can throw a cam sensor, crank sensor and TPS at that engine
for less than $75, and about an hour labor.
Not saying do that, but it's a viable strategy for a DIY'er.
All these sensors and other electrical components degrade over time,
so new is usually best.
My wife's Lumina 3100 just threw a PO300, was chugging when hot, and
she smelled hot metal. BTDT with other 3100's. Bad coil or spark
module. Didn't even consider finding out which coil pack, or if it
was the spark module. Put all new in. Done, finished.
I can't believe he even considered replacing the ECU without checking
the wiring first. He probably knew the harness was bad earlier than
he said but held that so he'd have a good vid. Probably too good to
make that mistake.
But his purpose is to show scanner troubleshooting, whether it's
needed or not.
Good catch for geeks knowing the ECU sources 12v to
cam and crank on a shared circuit.
But that engine is basically a no-brainer for a moderately competent
DIYer since parts are cheap to throw at it.
Anything but an ECU fault or a hidden harness short is no big deal.

We see stuff like this more often than you'd think... scan tools really
have to be taken with a grain of salt. You really have to be careful, or
you can end up eating very expensive parts, and/or blowing more time
than you could ever bill for.


That's why I think the guy making the vid didn't charge for all the
"diagnostic" time he put into it.
ODB codes are great, and either pinpoint the problem, or give you a
starting point


This is why I say buy 'real' car's & trucks.

Erik

And which "real" car can't suffer degraded wiring due to neglecting an
oil leak?