Diagnosis: Getting Started Guide

Hello,

After reading so many interesting articles and posts featuring various model kits, I've somewhat lost track of everything.

To achieve a result as quickly as possible, which adapter would you recommend for a DIY project?
1) It should work with a Golf IV ALH engine (ideally, someone has already tried it).
2) Should be as easy to build as possible (e.g., using a breadboard).
3) Many people use VAG-COM. The trial version only allows for limited functionality (which should be sufficient for reading error codes). Can it also be used to record things like boost pressure values, or is the full version required for that?
Is it possible to purchase the full version without the adapter (just the software)?

Thank you very much!

Holger247 wrote:

which adapter would you recommend for a DIY project: 1) It should work with a Golf IV ALH engine (ideally, someone has already tried it). 2) Should be as easy to build as possible (possibly using a breadboard)

Hi Holger,

Christians' minimal adapter offers the simplest design, but comes with the highest risk of failure and limited protection against defects for both PCs and cars.

"Good functional safety with a slightly higher failure rate and higher construction costs, but still with easily obtainable parts, is what my 3.1 offers, for example."

IC enthusiasts are more likely to build Maik's version, which, thanks to MAX, generally offers slightly higher reliability, but is also more complicated to assemble for most hobbyists.

Mark's Adapter perfects this principle by focusing on "protection against voltage fluctuations from the vehicle's electrical system."

Adapters with (which are not readily available everywhere!) optocouplers offer the best protection against defects.
The standard circuit (according to Noxon) is simple in its construction, but does not offer a very high level of reliability.

My 2.4 offers increased operational reliability due to its adjustment options.

My version 4.0 offers an even higher level of operational reliability, albeit with a corresponding increase in construction costs, and should also be able to interface with vehicles that have two K-lines.

Nick's / Alex' adapter (not yet linked in the article) likely offers similar functionality without any configuration, and with better compatibility with "impossible" COM ports, although it requires slightly more effort to build.

So, choose something .

Hello,

I have a Golf IV ALH and I've modified Maik's adapter for my purposes so that it no longer includes the L-line (which doesn't exist in the Golf IV), but instead features optocouplers, making it galvanically isolated, because I use a 220V power supply in the car, and the MAX232 chip has failed twice with Maik's adapter. I've simplified it as much as possible because I don't want to solder complex circuits; this thing just needs to work. All the parts are available, for example, at Reichelt, and it's built on a breadboard, wired with 0.2mm enamel-coated copper wire (so it's directly solderable), and it works without any adjustments and is 100% stable for me, even with a P75 notebook. I've made the plans and pictures available here for free use.

Best regards, Gerd.

Thank you both!

Could someone give me a hint about point 3)?

@HGK:
Your adapter looks good. Is the schematic for your circuit based on Maik's design (with the exception of the L-line), or are there further modifications?
Woher hast Du den ODBII Stecker? By Reichelt?

Thank you.

Holger.

Hello Holger,

The transparent blue casing of the adapter is [url=http://www.conrad.de/scripts/wgate/zcop_b2c6e13574c/~flNlc3Npb249UDkwV0dBVEU6Q19BR0FURTAzOjAwMDAuMDJkZi4yZDA4NjIzOSZ+aHR0cF9jb250ZW50X2NoYXJzZXQ9aXNvLTg4NTktMSZ+U3RhdGU9MjU5NDM1MDc2Ng==?~template=PCAT_PRODUCT_DETAILS_DOCUMENT&object_id=0000000000000000000000000000000000522471&object_guid=E42DD83B3952E67CE10000000A010221&p_load_area=203036&text_ztab=Typ%401591+BTBU+%7cFarbe+%28transparent%29%40Blau+%7cAbm%2e+%28L+x+B+x+H%29+mm%40112+x+62+x31&page=5&hmmh_alt_image=%2fIMS_Docs%2f76%2f76C5953EECAEA88DE10000000A010251%2eJPG&p_selected_description=Geh%e4use+Bis+120+Mm+Kantenl%e4nge#l] here, which I bought from Conrad in Cologne. The OBD connector, which I bought quite expensively on eBay based on a tip I found, I mean it cost 15 euros for this plastic part.
The curves I recorded were all obtained using freeware versions of VAGCOM, and they include at least the first 20 data blocks from the engine control unit.
The circuit is the one designed by Maik.
minus
The Golf IV does not have an 'L-Line' trim level.
The driver transistor for data reception is not necessary in this case.
plus
2 specialized optocouplers and a small DC-DC converter (a great piece of equipment, a bit more expensive) to power the MAX232.
A different LED configuration is needed so that the receive LED only indicates data reception.
and
not to mention.
the blue voltage LED in the transparent blue housing (a must-have for the Golf IV) .

To do this, dust off an old laptop (mine has a Pentium 75), a VGA screen with a resolution of 640*480 is ideal, and you'll need a power supply for the car and VAGCOM for automatic startup .


Well, of course, something has to break on the car so that men have something to tinker with.
At least, I once properly cleaned my Mass Air Flow sensor (picture here), after 115,000 km. It was an ALH engine, specifically the side that is exposed to incoming air, i.e., the area where you can't reach without removing the sensor, using a Torx screwdriver with a hole in the middle, from the pipe fitting. I recorded the before and after curves. Afterwards, the values were back within the normal range , meaning that at full load, the smoke limit was again above the torque limit.
I used isopropyl alcohol for cleaning, but I think it's too aggressive. It's better, as Diesel-Gustav (I think his first name starts with H ) described, to use Pril diluted in water, because I only saw the finest soot, that stuff that we all have in our lungs .

@Everyone
I've been reading here for a long time, so I'd like to take this opportunity to thank Ulf and Michael II, and of course everyone else, not forgetting Rainer, the owner of the website. The interested layman (apart from Diesel-Gustav, who is probably an expert) is capable of amazing things, as I can see time and again when I read here (the last entry in the error database, written by Ulf, about the ticking sound when accelerating, is brilliant).

HGK wrote:

Diesel-Gustav (I think his first name probably starts with H )

Hi.

If you're thinking of H.F., I've also considered that possibility, but I think the writing styles of the two are quite different overall, so I'm not sure they're actually two different nicknames for the same author.

But it doesn't really matter - I'm just glad that "real" professionals like Gustav are also participating.