Get a cup of coffee, this could take a while.  Lots of people often ask me about automotive scan tools.  I use a lot of scan tools in my every day life.  Being an ASE master and instructor of automotive techs affords me a lot of exposure to a variety of different scan tools.  I get grants and use them to buy scan tools to train students on.  let me share with you some of my observations of how they differ.  We can look at the basic mind set when it comes to scan tools:

1) DIAGNOSTIC CAPABILITY

2) BI-DIRECTIONAL COMMUNICATION

3) ABILITY TO BE UPDATED AND HOW MUCH UPDATES COST

4) ABILITY TO RE-FLASH MODULES

5) FUNCTIONALITY

6) OTC MATCO & MAC Genisys, Deturminator, and Mentor

7) LAUNCH X-431?  Read this first!

8) Dont take my word for it, DO YOUR HOMEWORK!

1) DIAGNOSTIC CAPABILITY:

A scan tools ability to retrieve trouble codes, ability to aquire lines of data (Read sensor output and observe actuators like the IAC or TCC).  This level of information is common to almost ALL scan tools to varying degree.  What do I mean by varying degree?  Lets take for instance, an OTC Genisys.  Pound for Pound, it used to be the best value in an all encompassing scan tool for the generic non dealer mechanic.  It provides a pretty good number of lines of information for, oh say, a 2000 Chevy Blazer.  You get like 30 lines of information in data stream and it can be graphed or gauged at the uses choice.  Now lets look at the same vehicle only with a Tech II (The dealer specific scan tool).  You get about 1/2 more lines of information of not only the vehicles PCM, but BCM, Radio, and all other on board modules.  Tech II offers far more lines of information in more vehicle modules and modalities such as being able to look at the operation of several vehicle systems independent of the PCM or BCM.  You can see dashboard functions, radio functions, power seat functions, ABS functions, and Transmission functions if far more detail.

In other words, OTC Genisys, Snap On Modis, ACTRON, Nemisys,and AutoEngiinuity as well as all the others do a pretty good job of giving basic information on a lot of applications.  TECH II, Miller DRB, Miller StarScan, Ford WDS, Ford IDS, Hockock NGS, and so on, offer a lot more lines of information and in their respective diagnostic modules independent of the PCM.  You can look at them alone and see what is going on during operation.

Having functions or being able to attach external functions like a lab scope or exhaust gas analyzer are a huge benefit as well.  Not all scan tools allow you to do this.

2) BI-Directional Capability

This, simply stated, is a scan tools ability to communicate in both directions with an automobile.  Imagine a scan tool as a telephone.  If you could only hear what is on the other end, but could not respond or talk back, you still have a valuable source of information.  This is what 90% of scan tools do, they tell you things, but you cant talk back and make stuff do stuff. 

With Bi-directional ability, you can, for instance, activate the ABS motor in a car, you can pop the trunk open electronically with the scan tool instead of the key or button inside the car.  You can turn on headlights, you can make the fuel gauge sweep from empty to full.  You can actuate the IAC in specific amounts to check its function, You can open or close the fuel injectors with a pressure gauge hooked up to the fuel system to detect blockage or clogging of the injectors.  You get different degrees of bi-directional ability through generic scan tools like the Genisys or others. With most generic scan tools you get NO bi-directional communication capabilities.  With the dealer specific scan tools like Vetronics Tech I and Tech II, Miller DRB, Ford WDS and IDS, StarScan, and some others, you get an much more broad bi-directional menu for diagnostics and testing.  A great example of why bi-directional communication is imperative for todays tech. is servicing ABS systems.  To bleed the brakes on some cars, you must have the ability to put the ABS unit in a bypass mode.  This allows the mechanic to temporarily open the control valves in the ABS unit up so brake fluid can flow through it and all the tech to get any air out of the system.  It can also allow you to open the accumulator up to get air out or empty it.  You cant do this with the cheapie scan tools, come cars allow you to do it manually, many do not. 

Look hard at some of the OBD II/ CAN readers on Ebay that are PC based (can be used with a laptop or desk top PC) or for use with a PDA.  The upside to these set ups are that the average PC is light years faster than the average scan tool communication rate.  Most scan tools use old serial connections and are very slow comparatively.  NOT ALL PC PROGRAMS ARE CREATED EQUALLY!  Some hardware kits have the software built right into the connector harness like the OTC Palm Scan that is used with the very antiquated Handspring Palm Pilot. Even though it is very old and by todays standards very slow, it is still better than a lot of dedicated scan tools built today, BUT it has no bi-directional communication ability.  Other PC based systems like AutoEnginuity actually provide bi-directional capability.  MAKE SURE you ask the seller EXACTLY WHAT BI-DIRECTIONAL COMMUNICATIONS THE PROGRAM IS CAPABLE OF. ATERRA lets you do Evaporative Emissions solenoid tests only in Bi-Directional mode.  Most wont do ABS, IAC, BCM Or Fuel injector functions. The only beef I have with AutoEnginuity is that they push the basic kit that does not do much for $200.00, but in the same ad, they dont tell you anywhere clearly that that does not include the "bells and whistles" program.  They muddle up the adds to make it look like they offer the all inclusive set up. The set that has "dealer level" functionality is over $1500.00.  For a little more, you could buy a whole scan tool that will do the same thing and actually get the hardware too. 

3) UPDATEABILITY 

Just like any investment, YOU BETTER READ THE FINE PRINT as to what these kits come with!  Many sellers out here and abroad will extoll the virtues of their products, but are actually selling you a scaled down coverage kit that will need to be expanded to include all the stuff they are advertising. 

MAKE SURE YOU KNOW HOW MUCH SOFTWARE AND FIRMWARE UPDATES WILL COST YOU IN THE FUTURE! This is a real sore spot with me.  Launch X-431 advertises cheap yearly updates, usually for less than $40.00.  What they dont tell you is that is $40.00 PER CAR LINE!  That means that an update for GM (Which does not work for a damn in X-431) will cost you almost $40.00 and so will every other car line you want to update.  Compared to OTC Pathfinder, European or Asian updates, that is a pretty hefty price to update your scan tool!

Other scan tool manufactures like Snap-On make you buy updates for scan tools liek MODIS, but you can negotiate with the tool truck guy to get free updates for many years where you cant do that here on Ebay, BUT if the price is right on Ebay and you have a reliable seller, the cost savings may outweigh the additional cost of updating the unit.  Its a personal choice but as I said, MAKE SURE YOU KNOW WHAT UPDATES WILL COST!

4) Module Re-Flashing capability:

This refers to a scan tools ability to be used as a programming tool for a vehicles PCM, BCM, TCM, Radio or any other module or device on todays cars.  Lets take the example used earlier of the 2000 Chevy Blazer.  If you need to change out a radio, your in for a big surprise!  Once you try to put a radio from another vehicle in the Blazer, it wont work!  You have to re-flash it with the new vehicles VIN # before you can access it.  You cant do this with a Genisys.  What if you need to put a new PCM in this truck?  You CANT INSTALL A USED PCM IN THIS TRUCK!  All used PCM's have the VIN # from the vechile it as programmed for on it.  Some times they will still start up but you usually will not get full function or the Service Engine Soon light will remain on.  Cars and trucks do all kinds of funky ass stuff when you start mixing and matching PCM's.  So now what do you do?  If you have a scan tool that allows you to re program PCM's or BCM's or Radios or whatever, you can re-flash those modules with vehicle specific information and VIN #.  Your going to need more than a scan tool, however, you will also need a program that will allow you to get programming.  Its kind of like a Windows update on your PC.  If you dont have a valid license code, Microsoft will not allow you to update or sometimes even install the software.  You have to go onto the Microsoft website to get updated information for your particular version of windows.  Re-Flashing ability is much the same way with a scan tool.  IF a PCM freaks out on that Blazer, you need to go get a blank from the parts store or dealer, put the vehicle VIN code on it, download the most current programming from a computer onto the scan tool, than dump it all onto the new PCM.  Often times manufactures offer alternative programming to overcome specific problems with a particular vehicle.  If you were flashing that OO Blazer I was referring to, you would find a few PCM reprogramming profiles to address pre-ignition problems when the engine is hot or you can choose the standard programming.  In extremely hot climates, some of these trucks "ping" on acceleration with the addition of drag from the Air Conditioning.  The new programming adjusts for this by changing the timing profile when the AC is on. You can also change speedometer calibrations for gear ratio or tire size, re-flash a radio so you can install it into another vehicle, or re-flash an ABS module.  The possibilities are unlimited!   

Some generic scan tools allow for module re-programming.  OTC Genisys lets you re-flash GM PCM's if you buy the very pricy software and yearly subscriptions.  Tech II will do GM's great but again, you need to also have access to GM TIS program to aquire the necessary vehicle programming to re-flash a module.  99% of generic scan tools do not let you re-flash a module.  The ones that do also require software to do it so be mindful of this when you decide what to buy.

5) FUNCTIONALITY

HOW GOOD IS GOOD ENOUGH AND CAN THE SCANNER YOU BUY DO WHAT YOU NEED IT TO DO?

Many scan tools that are generic are not updatable and operate on a generic OBD II or CAN platform.  This means that they will work with just about any vehicle pretty good but only offer you limited ability like reading and resetting fault codes, accessing basic datastream information from the PCM. They seldom offer bi-directional communications and module re-flash capability.  Some PC based systems are great for looking at Data Streams as they allow functions like graphing and the ability to look at "Snap shop" information.  Snap Shot information is what is stored in your vehicle computer when a fault code is set.  It takes a picture of what was going on when the fault occured so you can more easily detect the problem and its contributing factors without having to drive the care for a half a day to see what was going on when the Service Engine Soon light comes on.  Generic scan tools seldom offer this capability!  A good scan tool offers you the ability to also look at "Pending Codes." these are fault codes that occur, but not enough times to trigger the Service Engine Soon light. There are a few modes of fault codes. A type A fault code, for instance, is a major malfunction of something that will quickly cause a catalyst failure.  Something like a misfire will trigger a flashing Service Engine Soon light and set a code (or several).  Some codes will set only after the ECM sees the problem two or three times in a specific amount of time, like a bad Oxygen Sensor code.  It does not immediately trip a Check Engine light unless it is taken off line completly (comes unplugged or circuit fails).  Code history function allows the computer to record "hiccups" that occur but only intermittently.  You could have a bad O2 sensor that only goofs up once every couple weeks but otherwise works fine.  The check engine light wont come on until it goofs up several times in a specific amount of time and under certain conditions.  When a "hiccup" occurs, a car will record the fault and a snap shot of what occured with everything else in the powertrain command module. This allows you to check the history to see what happen and what led up to it and what happened afterword.  Sometimes things like water entering a connector will set a "history code" but wont turn on the Check Engine light.  If no more problems occur in the next 40 warm up cycles, the code and its snap shot information go away.

What does all of this mean?  Make sure your scan tool is not just the most "economical" but make sure it can do all the things YOU need it to do of are going to need it to do in the future.  For instance, if your going to buy a new Dodge Durango, dont waste your time on a Miller DRB III For a Chrysler, it wont work!  DRB III will not read CAN communication which is on most cars today.  CAN is a network communication platform that not all OBD II cars have.  To diagnose that new Durango, you will need a Miller StarScan.  It has CAN Ability.  For GM, the Tech II by itself wont read CAN communications.  You will need to purchase a CANDi Module to allow it to communicate with the CAN controlled vehicle.  OTC Genisys has CAN Capability out of the box as does others like the Launch X-431 and Snap-On Modis.  Again, the difference is in the amount of information and functionality you get from the aftermarket vs. the dealer specific models.

Last thing here.....in some cases all scan tools ARE CREATED EQUAL!  If your looking at an OTC Genisys, it is EXACTLY the same as the MAC, MAC Mentor, and a few others who market their own versions of this same unit.  There is absolutely NO DIFFERENCE between the different name plate models of the Genisys at all! Just the price tag! When they break, they go to the exact same place to get fixed at the Owatonna Tool Company (OTC). There are some distinct differences between the Tech I and an OTC 2000 scan tool however!  They look the same, but the Tech I is bi-directional, the OTC 2000 is not.

6) SO YOU WANT A GENISYS? 

IF YOU ARE LOOKING AT AN OTC GENISYS, MAC MENTOR, MATCO DETURMINATOR THERE IS A FEW THINGS YOU NEED TO KNOW BEFORE YOU  BUY ONE USED ON EBAY!!!! 

There are a few models and software packages with Genisys.  The order model has very small on board memory capacity. It is the first model of Genisys and can be identified simply by knowing what kind of "ON OFF" switch it has.  IF its the square black power switch, DONT pay more than 500 bucks assuming its loaded with all the latest stuff and has a memory expansion card in it.  Those older units have limited memory capacity and will soon not be able to update due to the size of new Pathfinder and other programs.  They are cheap and if your looking for a unit for older cars, work fine, but dont over pay for it.  The second generation of Genisys has a 256 mb on board memory and the latest version has a 512 mb on board memory.  The 256 and 512 versions have a red oval shaped power button.  If you are buying one on Ebay, you had better ask the buyer what kind of power button is on the unit and what the ON BOARD MEMORY CAPACITY IS.  Lots of people expand the memory by putting a memory card in the side BUT you cant use just any generic memory card, it HAS To be formatted for the Genisys Operating system and you cant do that on your PC.  Finally, you need to know whether the Genisys has the old original operating system on it or the new VERSION 2.0.  There is a HUGE difference in the speed of the tool with the newer 2.0 vs. the old system.  Any Genisys can be updated to 2.0 and its HIGHLY recommended because nothing after 2004 will load onto the old operating system.  If you think your going to buy an old Genisys for cheap, and just upgrade it, think again!  If its too old, the new programs will not all fit on the older square black power button units. Also be aware that ANY programs loaded into your Genisys are resident to that unit.  Once a program is loaded onto your unit, it cant be loaded onto any other Genisys.  Be careful of buying items like a SCOPE MODULE or GAS ANALYZER for your Genisys if the buyer does not have or does not know if the smart card has been installed already.  You can buy them new from OTC or the MATCO or MAC tool truck guys, but they cost a couple hundred bucks.

7) THINKING ABOUT BUYING A LAUNCH X-431?  READ ON. 

Just for your information, this unit is made in China and, if you can believe it, there are actually knock-offs out there for it.  The X-431 seems to work great on BMW's and Benz's but they totally SUCK For domestics!  They have programming for the domestics, but 98% of the time, do not work!  If you service a lot of European cars, the X-431 is a great tool.  It works well with a lot of Asian cars too but for Honda's...THEY BLOW! Launch is having a lot of problems with software and subsequent updates.  You could have a version of Honda software that works great up to 2002, for instance, you buy the update to upgrade to 2006 and than NOTHING WORKS!  You have to go back to the old software to get your X-431 to read ANY Honda.  The X-431 Scan tool is not economically priced and for what you pay, should do everything and give you a reach around too!  It simply DOES NOT rise to the hype of being a premier all encompassing scan tool.  The X-431 Infinite scan tool is particularly problematic and should be thrown on the scrap heap!  The wireless module is as big as a house and offers absolutely NO ADVANTAGE in diagnostic ability and is often a impedance.  I have seen non blue tooth X431'switch the same programming work great on vehicles that the X-431 infinite wireless bluetooth model WONT READ! Maybe in a few years those folks at Launch will figure it out, but as for right now, unless you are working on a SEAT, SKODA, BMW, Benz, Sprinter, Transporter or VW your going to be very disappointed wtih the X-431. REGARDING X431 UPDATES........BE CAREFUL BUYING THIS SCAN TOOL ON EBAY from NON-FACTORY APPROVED VENDORS!  You need to get a VENDOR CODE to get your free year of updates form LAUNCH for your X-431. Without that VENDOR CODE, you CANT GET YOUR UPDATES.  YOU HAD BETTER GET THAT VENDOR CODE BEFORE YOU BUY YOUR SCAN TOOL OR YOUR GOING TO GET SCREWED!  Launch tells you point blank on their update site that most EBay Venders ARE NOT AUTHORIZED Dealers so you CANT UPDATE your scan tool if you buy from those unauthorized dealers.  The reason many are unauthorized is because they are selling knock off units are lower prices.  We got ours from an authorized EBay Vendor called USAtoolwearhouse and had no problems getting an update code. NO I DONT WORK FOR THEM.  We buy all our scan tools and software updates from them because their prices are the best, they sell top quality, authentic tools and electronics and stand behind their products.  NTX tools dot com (network tool wearhouse) is their on line company and sometimes you can get even a better deal from them than you can get from their Ebay business USAtoolwearhouse.

8) DO YOUR HOMEWORK SON, DO YOUR HOMEWORK!

Best of luck and remember, an educated consumer is any vendors best friend!  Dont be afraid to ask questions.  If they dont know or dont want to take the time to talk to you, DONT BUY FROM THEM! If they get crappy about answering your questions or take forever to return your emails, what happens if you have a problem later?  Your scan tool will be with you longer than most peoples spouses will in this country!  Its a long term commitment and investment that will make you money for years to come, so take your time and make a good choice.  Bargain shopping is great but if you want quality you can grow into for many years to come, you had better think about spending a little money! If your just looking for a code reader, you can get one of those for 25 bucks.  Dont throw away a lot of money for a glorified code reader if thats what your looking for. If your looking for something to grow into, and need it for a wide range of different cars, you still cant beat OTC Genisys, or Snap-On Modis. If your just doing GM's you need to get a Tech II and for old non CAN Mopar, its the DRB III and for CAN controlled MOPAR Its got to be StarScan.  For Old Fords its going to be either NGS, WDS and for the new Fords, Mazda and Jags its IDS.  Sure does get confusing doesnt it?

If you have a question about scan tools, just click on my Ebay Screen Name and feel free to ask.  I dont know it all, but I know a lot and maybe we can both learn something from your questions.