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Overview | Hardware readers | Laptop Interface | Mobile Device Interface
Diagnostic code readers and Scan Tools allow you to read Diagnostic Trouble Codes (DTCs) in your cars Powertrain Control Module (PCM) which caused your check engine light to come on.
A Diagnostic Link Connector (DLC) Allows the Code Scanner or Scan Tool to communicate or "plug into" your vehicle's computer(s). Usually under the dash on the middle or drivers side.
Onboard Diagnostics II (OBD II or OBD2, OBD-II) is a second-generation emissions diagnostic system required by the U.S. EPA on all 1996 and newer vehicles.
There are code readers available from your auto supply store for $70-$180 which will connect to a socket (port) under your dash and allow you to see a diagnostic code related to the problem which caused your check engine light to come on.
e.g. P0440 - "Evaporative Emission Control System Malfunction"
Mechanics usually charge around $70-90 to check the code for you, so if your only problem is a loose gas cap, a reader will pay for the code reader the first time you use it.
Some places distinguish between "Readers", which just read codes and "Scanners" which give you more information.
Note prior to 2008 there were several communications protocols in use.
In 2007 Consumer Reports tested some of these readers and said the following worked well.
Intermediate readers or scanners have include the ability to take a "snapshot" of the vehicle's operating condition at the time of the faulty code. That records things like engine speed and temperature to assist in diagnosis.
Advanced Engine Programmers Allow you to program your PCM to increase performance. Includes improved power or mileage, optimize for 87 or 93 octane fuel, Engine Rev Limiter, Cooling Fan On/Off Temperatures, Permits use of low-temperature thermostat for cooler, denser intake charge and lower engine operating temperature, Transmission Shift Points, Transmission Shift Firmness, Top-Speed Limiter, Speedometer/Odometer Correction.
Computer Interfaces allow you to connect your computer or Palm Pilot to the OBD port and perform the same functions as the stand-alone scanners.
VAG-COM is a PC/windows program for VWs and Audis developed by Uwe Ross (www.Ross-Tech.com/). It uses Volkswagen Audi Group's (VAG) proprietary diagnostic protocol and will only work in VW/Audi vehicles. In addition to showing fault codes and monitoring operating parameters, VAG-COM allows an enthusiast to make "adjustments," such as reprogramming the locks or the stereo, re-aligning the immobilizer after swapping ECU's and resetting service reminder indicators.
Software Available to Purchase
OBDLink Bluetooth Scan Tool at ScanTool.net $150
PLX Kiwi Bluetooth adapter for android $99
PLX Kiwi Wifi adapter for iPhone $149
ELM327 Vgate Scan Advanced OBD2 Bluetooth Scan Tool $20 - At Meritline