True, and independant shops can still scan the codes, diagnose the
problem, and fix the problem; but dealers in their attempt to gain back
a handle on the service industry have put in other things...like the
annoying service lights...that can't be turned off with normal readers.

No. Although the OBDII standard establishes fault code retrieval over
the various regional protocols it does not mandate access to proprietary
data stored in all the various accessible systems. OBDII is restricted
in that only codes in the standard table for powertrain management are
accessible and can be reset or cleared. There are six modes or levels of
access available in the standard that include monitoring and activation
of individual components via the DLC (data link connector) but only a
handful of scan tools have this capabilty mainly because of cost. The
run of the mill scan tool for diagnostic work on domestic cars and a
smattering of forign cars will run in the neighborhood of $10,000. That
is with software that probably will not be valid for much other than
code reading on cars built after 2002 or so. Software upgrades run on
average $3000-$5000 a year. For Volvo VIDA you can buy a three day pass
to access for one car for about $40.00, however, to download any info
you need a VCT2000 (Volvo special toll $1500-3000 depending on new or
used; a cable for connecting the VCT to the car another $1500) you must
be using a laptop with a 9 pin serial port, running Windows XPPro SP2 or
the VIDA software will not install. Now you can access, update, and
reflash any system on the car. And this is not unique to Volvo. SAAB has
their system, BMW theirs, Mercedes theirs, Land Rover theirs,
VW/SEAT/Audi theirs and so on, you get the picture. So yeah, the cost is
limited and even affordable if you happen to be doing around $3,000,000
a year in parts and labor. Otherwise, I would say it's somewhat
expensive or more likely prohibitive for most small independent shops.

Bob