Phil Breau said:
I am ok with using a computer and I'm ok with making simple repairs on cars.
I just don't know the first thing when the two are mixed. I want to learn
how to hook up a computer to a car and read and decipher codes. Can a laptop
work with a serial cable and special software,
If you have a 1996 or later vehicle sold in the USA, it is equipped with an
on-board diagnostics connector conforming to the OBD-II standard. It's
usually located under the dash, sometimes near the steering column. Older
vehicles usually had some form of this, but it wasn't standardized until
1996, with a few exceptions as early as 1995.
The OBD-II standard specifies a base set of codes and commands to which all
vehicles must conform in retrieving diagnostic information. Not all systems
in the vehicle are instrumented, but many are, especially the ones directly
related to engine performance and emission control. There are several
different communications protocols, however, and they don't conform to
RS-232, which is the serial communications standard used on a laptop. Also,
the various manufacturers have specialized codes which are a superset of the
OBD-II codes. For example, such codes might access diagnostic information
on a particular electronic transmission, or from an ABS system. A plain
vanilla OBD-II scanner probably won't be capable of retrieving these
specialized codes, although there is ongoing litigation to force auto
manufacturers to make the details of their specialized codes available to
third-party scan tool manufacturers.
As another poster has suggested, you can purchase scanner devices to connect
to this diagnostic port and read trouble codes stored in the computer.
These devices have a wide range of capabilities--some will only work with
one vehicle make, while others will work with a variety of makes. Less
capable models typically start new around $150-$200. Sometimes they are
quite expensive-ranging up into the thousands of dollars, depending on their
capability, but sometimes used units can be found on Ebay for less. And
yes, the dealer service departments have their own scanner devices targeted
specifically for the make of vehicles they service. These are usually quite
expensive.
There are companies out there selling computer interface kits and software
that allow you to use a computer to access this information. Prices vary
widely, but they're typically somewhat less than the dedicated scanners.
There are also similar kits you can purchase if you're handy with a
soldering iron to build a scanner interface yourself from components. I've
gone this route myself, and it's been an ongoing project, but I have
successfully read the codes using my device. If you're interested in
something like this, take a look at
http://www.scantool.net.
Many late-model Chrysler vehicles make some of these codes available via a
sequence of dashboard light flashes, or on models equipped with
electro-fluorescent odometers, usually 1998 and up, the odometer display can
be used to retrieve codes. There is a sequence of key-on-key-off-key-on
described in this NG's FAQ that will help you learn how to do this, along
with a description of the codes available. I'm pretty sure you can find the
FAQ at
http://www.allpar.com if it isn't available right now on your local
Usenet server.
Finally, you can visit any AutoZone store and have your vehicle scanned for
free. If you just want to fix your car, and aren't lusting for a new, cool
tool for your collection, or an electronics project, maybe this is the best
solution available. See
http://www.autozone.com for locations.
--Geoff
