On Fri, 1 Feb 2013 05:39:04 +0000 (UTC), gregz
wrote:
wrote:
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.
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.
This is why I say buy 'real' car's & trucks.
Erik
PS, Incidentally, this 'ScannerDanner' guy has many superb automotive
computer related troubleshooting video's up on YouTube.
Like I said - the scanner does not tell you what to replace. It tells
you what is wrong.
It says the right bank is lean, or the left bank is rich, or the left
bank front O2 sensor is slow, or reading low.. It is up to the
mechanic to KNOW what will cause those problems. And how to find /
eliminate the possibilities without throwing the parts department at
it. Do you have a bad injector? or a vacuum leak? Or is the engine
burning oil?
Or the scanner tells you you have an intermittent misfire. Or a
misfire on cyl 5. What is causing the misfire? A bad plug, a bad wire,
a bad coil, a vacuum leak, a bad injector, a bad valve? At least you
know to look at #5 cyl, not 1, 2, 3, 4, or 6 (or 7 or 8)
It is the combination of codes and/or other symptoms, together with
the history of the vehicle, and knowing what goes wrong on certain
vehicles.
You did not have that ability on the older cars - Yes, you could hook
a scope to it - and if you knew how to read both the primary and
secondary patterns, the vacuum guage, the dynamic compression test,
etc it COULD give you most of the information. But not everyone had
the money and space to have an analyzer scope. Every DIY shadetree
mechanic can afford a basic OBD2 scanner, and it will fit in the glove
compartment (or even the ash tray)
The mid-year stuff - electronic controls but pre 1996 (pre OBD2) every
vehicle needed it's own specific scan tester - some gave lots of good
information, and others were almost useless. Some would blink the CEL
when you connected the right combination of pins/wires on the test
plug to spell out the code.
In trying to fix a 1995 olds with OBD 1.5 , had troubles. First was
question on reading the computer. Later found it faulty, replaced with junk
yard $35 unit. I had trouble trying reading first computer as well as
shops. Intermittent problem giving codes. Sure the intake gaskets first
needed replaced. Intermittent. Giving crank sensor codes. Still problem.
Turned out to be intermittent spark control module. The sensors go to the
spark control module.
I bought OBD 1.5 USB plug in, but had trouble communication. Never got to
test again after computer was replaced. Shop took over.
Pre 1995 gm vehicles had less computer info. To add confusion, there was
more than one version of OBD 1.5
Actually, I could read MORE information from my 1988 Chrysler and 1990
Aerostar than I can get off the new OBD2 vehicles - but it was raw
data that I had to interpret by myself. I could read the value of
every sensor - but the scanner had no idea what was correct, or within
range, so it didn't give a code saying "check this"
Greg
Actually, officially, no such thing as 1.5 You had all the
non-standards that were machine specific that fell loosely into OBD1 -
then there was draft OBD2 or what we in the trade called "pre-2" -
basically just GM trying to get a jump on the technology, then OBD2.
Anything before the full OBD2 of 1996 was a bit hit or miss. My Auto
X Ray scanner has 5 lead kits -OBD2,OBD2 manufacturer specific, GM,
Ford and Chrysler. Each of the imports had their own "flavour" as well
- I didn't bother buying any of them The "manufacturer specific" was
for 1995 GM vehicles with OBD2 plugs that were not fully OBD2
compliant.