Pretty much everyone on the forums agrees that it's not worth messing around with anything other than VAG-COM. On a friend's advice I bought a knock-off Chinese cable from eBay and tried, unsuccessfully, to get the old shareware version of VAG-COM working under Windows 7. I tried a whole host of different compatibility options and whatnot but I could not get it to run. VCDS lite worked fine, but is rather limited.
The only other option seemed to be a full version of VAG-COM, however I'm quite mercenary and a proper VAG-COM setup is hundreds of pounds. The wife would be hassling me about why I needed to spend all this money on that dopey car already, what a total money pit it was, etc. Still, pretty much everyone stands behind VAG-COM - it's a great product, kept up to date, and from what I understand the lifetime support is brilliant.
Anyway, one night I was flicking through Amazon when I saw a handheld VAG-specific code reader. I had a look, as much to chuckle at how ropey it would be as anything. I mean, it's £40 - it's going to be garbage, right?
Surprisingly, though, as I looked through the screenshots and user contributed photos I found myself getting quite interested. The menus looked surprisingly familiar - i.e. very VAG-COM-esque. The layout was slightly different to make it fit into a handheld screen but clearly identifiable.
The reviews made me a bit sceptical - there weren't many bad reviews, most of them were glowing - but with a note saying "I got this for free in return for an honest review". I'm pretty cynical so that's a red flag for me. In the end the pictures and the few non-freebee reviews swung it for me and I bought the unit. Here's how I found it.
Note - I've also created a short YouTube video tour of the device if you can't be bothered reading the rest of this!
In the Box
Inside the (slightly tacky looking) box you get the handheld unit itself, a 1m OBD cable, a USB A - mini B cable and a USB micro-SD card reader, for working with the 128MB micro-SD card which is pre-installed in the handheld unit.
There's also a manual, but the less said about that the better. Suffice to say, it shows you how to do everything you could figure out yourself (setting fonts, contrast, etc) and nothing at all about how to get stuff done (i.e. taking readings, clearing codes, setting adaptations).
First Impressions
The reader itself is powered from the OBD port so there's just the one cable. The screen is backlit and the default font and contrast is clear making it easy to read in anything from bright sunlight to pitch black darkness. The controls are pretty intuitive - the arrows move the cursor around and occasionally select digits, enter and escape do what you expect them to. Helpfully, if you have a list that is several screens long then pressing left & right effectively does a page up / page down. The keys are chunky enough to not be fiddly and press reliably, overall it feels pretty responsive.
Once the splash screen clears down, the first menu you encounter gives options of "Diagnostic systems", "Rapid scan system", "Channel number function" and "Special Function".
Most of what you want will be under "Diagnostic systems", this is where the options are to read and clear fault codes, read measuring blocks, set adaptations and re-code modules.
The "Rapid scan system" doesn't seem to work on my car, I assume it's supposed to dump out all the fault codes from every system a bit like VAG-COM's automated scan. On mine it just says it's unavailable.
The "Channel number function" seems to be there for certain tasks such as putting xenon lights into maintenance mode and so on.
"Special Function" has all sorts of functions from service interval reset to air bag (de)activation, throttle adjustment, and (supposedly) remote programming. I can vouch for the service interval reset as my mechanic forgot to do it when he did the last service.
Updating
I'd seen some misery online about getting updates for the VAG401 so one of the first things I did when I got it was try to update it. To do that you have to download Xtool's updater app, which made me a little skeptical, and the poxy thing only runs on Windows. As other reviews report, though, you don't have to sign up for an account to use that - it just requires the serial number and password for the unit which is found by escaping all the way to the very top level menu then selecting "About".
The firmware seemed to be up to date on mine straight from the factory, a late 2015 update if I remember correctly. So it doesn't seem to be bleeding edge current but certainly way more up to date than my 2002 car!
Updating was easy, I just took the SD card out of the VAG401 and put it into the reader that came with it, fired up the software, entered the serial and password and it automatically updated the software on the card. Seemingly it always downloads a new copy of the "display" module, even if you're current, and annoyingly when you check the "About" menu following an upgrade it seems to show you the "display" version rather than the diagnostics version, so it looks like you're not up to date even when you are.
A word of caution, here - when you update the software and start the VAG401 back up, it seems to upgrade the software as you enter the relevant sections of the menu. So for example the diagnostics update when you go into the "Diagnose" section for the first time. This only takes a few seconds but I'm guessing it would be pretty bad if you powered off while it's doing this. I made the mistake of doing this while on USB power - as other people have reported the USB port is rubbish on my VAG401 and if you look at it the wrong way it loses power. I don't think I've ever been so still as when I saw it flashing the firmware on USB power. I wouldn't recommend taking that risk but would rather suggest that you plug it into your car for a more reliable power source.
Finding / Clearing DTCs
At least half of what you want from a device like this is the ability to check for and clear diagnostic trouble codes (DTCs). As I mentioned the automatic sweep of all systems does not seem to work for me, I'm not sure whether this is the car (2002 TT) or the VAG401, however all the sub-systems can be checked and cleared individually.
If any fault codes are stored then the count is shown. Pressing enter moves onto the actual fault detail and moves onto the next fault code if there are multiple.
Back in the module menu you can select "Clear Fault Codes" to blow away all the DTCs in that module:
Press "Enter" to confirm:
Finally, just check they are really gone:
One good thing with this is that the sections appear to have been ripped straight off from VAG-COM, including the numbers, so troubleshooting advice from old forum posts is easy to follow even though you're using a different system.
Data Blocks
Reading live data with the VAG401 is pretty similar to in VAG-COM, the obvious limitation being the size of the screen. The locations of each data type is defined by the ECU rather than the reader so these are obviously the same whatever system you use to access them.
Simply navigate to the relevant module, select "Data Block Measurement" and enter the channel you want to view:
Most of the stuff that I've had use for has been correctly labelled in the VAG401, even moderately obscure sections like requested vs. delivered boost were properly identified on screen. The refresh rate isn't configurable but seems to be about once or twice per second depending on what you're looking at.
Adaptations
This is one of the not-so-well documented areas of the VAG401. As soon as I got the reader I wanted to make a couple of changes - first of which I wanted the scales and needles always lit on the dash (just the needles did this when I got it). As it happens, this setting is a straightforward adaptation which the VAG401 can do.
If you decide to do this, it is AT YOUR OWN RISK.
Basically I just had to go into the instrument section (referred to as "Dashboard" in the VAG401, but luckily still numbered 17):
Selected adaptation, picked the right channel (in this case 19):
The VAG401 will show you what that channel's current adaptation settings are:
Then allow you to enter a new value:
After confirming the value you entered it will push the value to the control module:
Note - the pictures show me changing it from 30010 (full lit) to 10010 (needles lit) just to demonstrate the process.
According to various guides on the Internet, all I had to do was change the first digit. This is easily done as when you open the adaptation channel it shows you the existing setting and you can just move left and right between digits, using the up and down arrows to adjust as necessary. It worked a treat for me but as everyone else seems to say, try at your own risk.
Module Coding
The other thing I really wanted to do was to enable automatic door locking. It's hardly downtown Johannesburg around here but I think it's a Module re-coding is not quite so user-friendly. When you enter any sub-system in diagnostics mode, the VAG401 displays various information such as serial numbers and also the current module coding - denoted by "COD". According to every guide I've seen you need to write down the original setting before you even think about changing anything!
Now, there was a load of decimal to binary conversion necessary to figure out what coding was necessary on the module, and separate guides are available to cover that. Read up carefully if you want to do this as mis-coding a module can make it inoperable. I took the original coding and ran it back through the decimal / binary conversion to make sure it reflected current behaviour before I started as a sanity check.
The coding itself is pretty straightforward, you just go into the relevant module (central locking in this case):
Then "Code Module":
Annoyingly it doesn't show the existing code but rather all zeros:
Just use left / right to choose the digits and up / down to change their values. Pressing "Enter" immediately codes the module without any confirmation, which is "efficient":
If you panic and hit enter too soon you can write a totally invalid code to the module. I know because, erm, a friend told me. Luckily in that case the ECU refused the bad code but you may not be so lucky. What I would say is be sure what you are doing before you even start, and again be aware that you do it all at your own risk. However, the feature is there and it does work.
Other Functions
The VAG401 has various other "special" functions available, such as airbag (de)activation, throttle adjustment and service interval reset.
The only one I've had reason to use so far is the service reset as the dash wasn't showing "SERVICE NOW" when I had it serviced, so the mechanic didn't reset it. As ever it's straightforward, enter the "Special Function" menu and select "Maintenance Reset":
Pick your model:
Job's a good'un. Not exactly the "one click" reset it claims on the box but there we go!
Summary
It's by no means perfect but the utility of the VAG401 is incredible - this is the best £40 I've ever spent on any car related thing. It permanently lives in my boot thanks to its small form factor and as far as I'm concerned it has paid for itself already in a month's use by completing a laundry list of tasks for me. It ain't VAG-COM but it is small, cheap and very functional.
