With the tremendous feedback I have received from the previous posting on scan tools, It has been suggested that I post another guide on J2534 and J1850 generic Pass Through devices.  I have been spending some quality time with several J2534 and J1850 units and some different software programs that actually allow the user to use a J2534 or J1850 unit as a generic scan tool. 

Please forgive the typos and spelling errors.  Ebays SUCK A$$ spell check does now work half the time and you cant cut and paste this stuff from word.  I am no scolor so please bear with me.

First of all, what is a J2534 Pass Through unit?  Its a device that allows its user to interface with a vehicle programmer using a PC or other device that can store or access flash programming media and re-program a vehicles modules.  In other words, its a go-between for a computer to communicate with the car's PCM, BCM, Security module, or any other module for that matter.  There are two common data paths for vehicle module re-flashing or calibrating.  One is to use the internet and purchase flash programming from manufactures, the other is to have flash programming information resident to the PC or on a CD or DVD and use that program to provide flash programming information.  For example:

GM TIS used to be available on DVD.  All of the Tech II updates and Flash Programming information updates used to come via DVD to its GM North American Operations and Saturn dealers.  Dealers would go on line and update TIS.  Every few months, GM would send out new DVD's to update the computers and update its data base making it able to get internet updates.  This was GM's way of keeping the independent shops from getting free updates via the net. Of course, dealership folks would get the old discs, post em on Ebay and sell them keeping the general public updates or near updated, and at least one quarter behind.  We used to have to use the Tech II to store and program flash data and draw VIN info from the car, take it to the PC, look for new flashes or corrective flash programming, put IT on the Tech II memory card, than disconnect it again and take it back to the car and dump the info on the controller. 

Now, there are no DVD's any more.  Now, you must pay money and to to TIS to WEB and pay for access to tech II updates and current flash programming.  GM sells it for days, weeks, months and years at a time.  This allows the user to access all of the stuff the dealership can get thier hands for a price.  Now, we can simply use a J2534 Pass Through to link the PC directly to the controller cutting out the need for the Tech II for flash programming. There are two ways to get the flash programming from the internet or a resident program in your PC to your vehicles programmer.  One is through a particular companies device (Tech II,  DRB III, Ford NGS,etc) and the other is with a generic or OEM J2534 Pass Through unit.  Today, we are going to focus on the J2534 method of programming.

J2534 is simply a protocol that, simply put, allows the user a mode to transfer data from a storage device to the vehicle programmer.  There are a lot of protocols for data transfer on cars.  For instance, J1850 is a protocol for diagnostic information transfer (a scan tool).  Datastream and fault codes are transferred through J1850 bus protocol. From this point forward, we refer to datastream information (IAT, CTS, O2 information etc) as PID's (Perimeter ID's).  You cant transfer flash data through a J1850 bus, you can only look at PID's and fault codes.

Ok, OK, now the acronyms are getting harry, but hey, you asked for it!  Remember, this stuff seems pretty complicated, but like getting into cold water in a pool, once your in for a few minutes, its quite comfortable.  Stay with me for a bit and just take it easy and slow.

Just remember, J2534 is for transferring flash data, and J1850 is for regular scan tool stuff like PID's and trouble codes.

The beauty of a generic J2534 is that you can flash ANY car sold in the USA with a generic J2534 unit.  By law, all manufactures of cars in the USA must make data for controllers available to the aftermarket so all of us can get it, most of the time, we just have to be willing to pay for it.  I am going to discuss how to pay for it and also, how to get it for free (or at least close to free).  You can also use a J2534 as a generic scan tool for J1850 communication with the use of some simple and cheap software.  OEM pass through units like Ford VCM, GM MDI, and Chrysler ScanMobile are very all inclusive and do way more stuff than generic tools, just cost a lot of money and just work with that companies family of vehicles.

So now you have your PC and access to the net a credit card to buy flash data and web addresses, now what?  You need a J2534 Pass Through unit.  The three I have used are the DrewTech CarDAQ-Plus, the Carden unit and the Snap-On units.  There are plenty of others including the Chinese ones that are dirt cheap and many times do all the stuff the expensive ones do, just built like crap! You can check out any of the units I mentioned by just doing a Google Search for them.  Personally, I live the DrewTech CarDaq-Plus.  Its very reasonably priced, and does all the stuff I love and best of all, its all DrewTech does.  The technical support is unsurpassed and the tech's there are friendly and guess what!  They are not in India or Pakistan, but right here in Ann Arbor Michigan.  They all speak english and know their product! Its a bullet proof unit and very simple to use and hook up. The Carden unit is a great unit, but Carden makes a lot of stuff and is a VERY big company!  Their company uses a call centers all over the world, enough said? If you happen to be on a tight budget and only need to flash one family of vehicles, you can look at the DrewTech Mongoose units.  They are compact J2534 Pass Through units that use USB and can do flash programming for just one or two families of vehicles at a fraction of the price of a all in one unit like the CarDAQ.  You can also get a ScanDAQ which does not require a PC, its a self contained unit with touch screen for doing any vehicle.  Again, a 100% AMERICAN company that builds their unit in AMERICA and has its support in AMERICA that sells high quality items at a competitive price.  You cant go wrong!  Before you ask, NO, I dont work for DrewTech, but I have bought several of their products and found each one to be a great unit.  The one software problem that caused me to call DrewTech took almost two hours and the tech line engineer was nothing but gregarious and helpful.  I called Carden for some information on how to configure a part of their driver program and was transferred four times and ended up with a person who handled master cylinders in Bopaul India.  Needless to say, I ended up calling DrewTech and they helped me configure the Carden unit!  LOL!!!! Ya gotta love it!

I have also used the GM MDI pass through unit.  It is simply a J2534 unit for flash programming on GM vehicles, nothing more.  No scan tool functions, no bi-directional, just a J2534 for GM's. Its VERY highly priced for what it does but works great on the GM's.  Fords VCM is a Pass Through but it must be updated every year for 500 bucks and will also do J1850 stuff to the max!  VCM does bi-directional, PID, and damn near anything you could possibly need for Ford applications (Ford, Mazda, Lincoln, Mercury, Land Rover, Jaguar). As far as OEM scan tools go, Ford IDS is simply the best all be it expensive to buy and maintain!  ScanMobile is also Chryslers all inclusive Pass Through.  They all have them folks, they just cost a lot of $$$$ but have a lot more functions than the generic stuff (with the exception of MDI).

Once you get the unit unpacked, you simply install the drivers and its off to the races! Now, you can go on line to, for instance, AC Delco TIS to WEB Or Motorcraft or Chrysler Techauthority and buy some flash programming access. You can also get your hands on some of the old TIS on disc programs or Toyota disc or ITIL/ISIS and load the program onto your compute. You can configure the IO management on the GM TIS on Disc to be able to transfer data stored on the PC through the J2534 and onto the vehicle controller.  You can also do this with Toyota TIS on Disc and several others that support J2534 functions.  I have not figured out how to configure ford IDS DVD programming disc calibrations to use with the Generic J2534 units, but I am hoping that one of you have and will share it with me! Some programs, like Toyota's will configure themselves for J2534 or scan tools like MasterTech, others like GM TIS require the user to manually configure the program to recognize a generic J2534 pass through device.  Once its configured, you can flash a controller in moments! The program simply walks the user through the process. 

Like I mentioned in previous articles, make sure you have a reliable filtered power supply on your battery before flash programming ANYTHING! If your vehicle power output goes below 12 volts, you can damage the controller rendering it un-useable or even worse, corrupt the programming causing all kinds of crazy stuff to happen.

Once you have your J2534 unit all booted up, you can compliment it with one of any generic programs that allow you to use it as a PC based scan tool.  There are a million programs out there that you can use but I like a program from Palmer Performance called PCM Scan. You can go to the Palmer Performance web site and down load a trial version.  Now, you can always go onto Ebay and buy one of any J1850 generic modules that will allow you to use programs like PCM scan as a all encompassing scanner.  Some programs have Bi-directional support but not all J1850 units support bi-directional communications.  Just like J2534 units, J1850 units can be had for very little money and provide you with access that far surpasses any self contained scan tool and works much faster as these J1850 modules are PC based.  Most aftermarket J1850 programs like Palmers PCM Scan can be configured for use with J2534 units as well as all the popular asian garbage J1850 units.  Remember, the pass through unit is just a go-between. The unit will only work as good as the program you are using but will inevitably be the bottle neck of information between the vehicle controller and the PC.

THE SNAP-ON NEW PASS THROUGH J2534 DEVICE CAN BE HAD FOR A LOT LESS FROM ITS ORIGINAL MANUFACTURER! 

Finally, I just added this little tidbit on Sunday Sept. 27 09 after getting to finally see the Snap-On J2534 generic pass through unit yesterday.  I would love to tell you how great it worked (it did) and how smartly built it is (it is) but I wont do that.  I wont do it because, like so many other Snap-On items now a days, its not their unit.  Its a DrewTech CarDAQ-Plus unit, nothing more.  As a matter of fact, they are charging about 400 bucks more for the same unit than DrewTECH is and giving you less memory and no generic scan tool program with it like DrewTECH does.  It does, however, have a nice black case and a nice Snap-On sticker on it. 

Like their hand tools, it is fair to assume that most people will buy the Snap-On unit for one of two reasons over buying it from its OEM.  Reason #1, Snap-On credit!  Snap on's tool truck credit rates are usually better than those of a credit card, which most would use to buy from the OEM.  Reason #2 is simply put, the same reason why someone would buy a Snap-on tool that is made by a company like OTC just repackaged and has Snap-on's name on it, they like to have all Snap-On's stuff in their Snap-on box.  To some of you, this may seem silly, but unless your a "snap-on guy" you would never get it!  Some would pay more to have a tool by no other name and thats that.  If you want to delthe into the psychology of this, I would be happy to post another guide on "the mind of the Snap-on only auto tech." I would like to think every mechanic would be smart enough to buy a tool from its original producer for almost half the price, but its not about being smarter or dumber.  Its about that fact that many times, a tool is built to Snap-On's more exacting specification by a manufacturer who may produce one of their own.  A good example of this is the face that Snap-On contracts Channel-Lock to build their pliers and cutters, but the Snap-On versions are made of better alloys, the cutters are designed differently and the handles are better for the Snap-On product.  The J2534 unit, however, is EXACTLY THE SAME as its OEM equivalent, maybe a little less in functionality for the money. 

I will be adding to this article as questions are raised and new information comes to light.  Please feel free to email me with questions, comments and expreacnes you have had.  Like you, I seek knowledge from these forums.