The Kit, minus the software man
For years we've extolled the virtues of Ross Tech's VAG-COM, an affordable way for professional and amateur mechanics alike to delve into VW/Audi on-board diagnostics systems. It's similar to the VAG 1551 and 1552 tools used by Volkswagen dealer technicians.
Now there's an additional aid of a similar type. Shade Tree Software has developed ProDiag, a powerful VW/Audi diagnostic tool based around the ubiquitous PalmOS handheld. PalmOS-based scan tools are not new, and many are designed to interface with an OBD-II connector and generate generic "P" codes. ProDiag is available directly from Shade Tree Software (www.shadetreesoftware.com) as well as from its worldwide distributors. For $249, you get the software, a manual, an OBD-II-to-serial interface and an activation code for one Palm device. A serial adapter cable is required to connect the OBD-II interface to a Palm, the wide variations in port configurations precluding a one-piece cable. Palm-to-serial cables are available from Shade Tree for an additional cost (about 20 bucks).
An adapter cable connects the Palm to a standard serial cable.
For those with pre-OBD-II cars (pre-1996) Shade Tree also sells a cable to adapt the OBD-II connector to VW's earlier 2x2 connector (often found under the shift boot).
Installing ProDiag requires Palm HotSync or dragging the software onto an SD or MMC card and copying. Once the software is installed, there will be a small icon of a car labeled "ProDiag." Clicking on the icon brings up a splash screen followed by a vehicle selection/connection screen.
Selecting a vehicle.
Click on the "Vehicle" button to select your car. If it's not listed, you can download an expanded vehicle profile from Shade Tree's website or autoscan the various modules on your car to create your own. Auto scanning communicates with the car's electronic modules to generate the fastest baud rate possible for each; it takes about 10 minutes. If you have a specific task in mind, you can scan only those modules you need. For example, I know my car doesn't have an on-board navigation system; there's no reason to go there.
Once a profile is selected or created, you can connect to individual systems; for instance, 01 is Engine Electronics. Each of the modules has a number of functions. For example, the 02 menu in the Engine Electronics module is to display and clear DTCs (Diagnostic Trouble Codes). When encountered, the codes write to the PalmOS Memo Pad.
Once a vehicle is selected, you can access the individual test modes.
Function 08, Measuring Blocks, is another popular function. It allows you to read the data collected by the vehicle sensors in real time. There is also a data logging and graphing function. The logging function also writes to Memo Pad and can quickly fills up multiple pad pages.
When you've cleared the codes and logged the data, you can HotSync the memo pad to a PC to import data into a spreadsheet for further analysis and better storage.
Having ProDiag handy, I have been able to diagnose a faulty thermostat, broken vacuum lines and a temperature sensor, eliminating the need to flatbed my car to the dealer. The proven capabilities of ProDiag will ensure its place in the glovebox.
The Palm HotSync program can display all of the ProDiag sessions.
System Requirements
•PalmOS handheld with OS version 3.0 or greater (approx. 350kB free space)
•ProDiag supports Palm, Sony and Handspring PDAs. Some, PalmOS 5.x devices are supported, in particular PalmOne Tungsten T line of PDAs and the Zire 71.
•PDA serial cable
•HotSync or removable media to transfer ProDiag to handheld
•VAS 5051/2 OBD-II to 2x2 connector (for pre-'96 vehicles)
The Good
•Small form factor, easy to carry in glovebox
•PDAs much less expensive than a laptop
•Affordable
•Powerful tool
The Bad
•Data logging to Memo Pad note is cumbersome
•Some car profiles must be downloaded from the web, or auto scanned, a time-consuming process
What's Included/Cost: $249
•ProDiag application
•ProDiag manual
•Serial to OBD-II adapter
•Activation keys for one PalmOS device
Logged data can be cut and pasted into a spreadsheet for generating graphs and better viewing. | 
Output from the Engine Electronics DTC menu. | 
Measuring Blocks can be graphed in real time. |