Diagnostic scanner for car

I have a GMC Envoy 04,(first vehicle) my engine light is on I took it at two different shops I received two different diagnostic and third if you count autozone. I would like to find out the diagnostic myself to know I am not being ripped off so which diagnostic scanner is best and what is the difference between obd1 and obd2, dtc
thank you for the help

If the problem is severe means you can diagonise yourself through some symptoms.. Otherwise you can't.. Better go to authourized service station..

Obd1 and obd2 are pinned differently at the connector.

If you know what they were reading here's the code definitions:

http://www.2carpros.com/trouble_codes/obd2/P1100

Automotive diagnostic scanners give car owners the opportunity and capability to diagnose their own cars without having to go to the mechanic.

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An automotive scan tool is an electronic tool used to interface with, diagnose and, sometimes, reprogram vehicle control modules.However, a typical scan tool does not have the ability to fully reprogram modules because it requires a pass-through device and specific software.

An OBD-I scanner that works with one make isn’t necessarily going to work with another. With OBD1, the goal was to develop a diagnostics system which focuses on the emission control systems of a vehicle. When it came to its effectiveness, the OBD1 was not really that successful in forcing drivers to pass the emission control system’s test.

OBD2, on the other hand, is a definite improvement to the OBD1. OBD2 has better signalling protocols and messaging formats. When used in emission control system tests, it can provide better results for a vehicle’s parameters.

Source : http://techprotools.blogspot.com/