Subject: Re: [Shop-talk] engine diagnostics

From: Wayne <[email-masked]>
Date: Tue, 06 Nov 2012 09:39:32 -0500

On 11/6/2012 8:51 AM, Matt wrote:
> can get basic code readers out of Asia for under $30, the growth of software
> in automotive function and control reveals that there is a whole lot more
> going on than what basic trouble codes reveal.  I think the answer will be
> (is) an OBD to USB cable and instead of a dedicated reader, the secret sauce

Yeah, putting it in software seems like it should make it easy & cheap. Know of any? There were a bunch of free-ware ones for my old pre-OBDII Nissans. Surprised there seem to be none for new stuff (but I haven't looked very hard.)

> That is what I had to get for my VWs and it is called VAG-COM.

Setting new standards in ease of communication with otherwise difficult to comprehend females! :)

-Wayne
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From: "gordies garage" <[email-masked]>
Date: Tue, 6 Nov 2012 10:01:14 -0500

I'll second an interface like VAG-COM.
I paid $99 about 11 yrs ago and have upgraded my dongle (cable USB 
interface) for about $40 IIRC.  I know I've saved hundreds if not thousands 
over the years on my '98 A4 and '03 A6 by being able to read the codes and 
take corrective action only if necessary, and clear the code for something 
unimportant.
One can also do some fun stuff like change the locking (ie: all unlock with 
one button push) and/or close all windows and sunroof with the lock button.
I believe as an investment in a tool that VAG-COM is well worth the money.
my .02

Gordie Bird

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From: "Matt" <[email-masked]>
Sent: Tuesday, November 06, 2012 8:51 AM
To: <[email-masked]>
Subject: [Shop-talk] engine diagnostics

> When I got my first relatively inexpensive code reader, I thought "great, 
> now
> I can peer into the control systems and maintain all my cars!"  It didn't 
> take
> long before I realized that wasn't necessarily the case.  OBD was 
> reasonable
> regulation attempting to standardize trouble reporting and while us 
> shadetree
> folks made out well, the justification for guvment monkeying with the 
> private
> enterprise of auto manufacturing was emissions.  Beyond a common interface 
> and
> the mandated basic tuning/emissions requirements, there was no attempt to
> standardize the rest of how your car's computer operated & reported. While 
> you
> will be the softwware that runs on your laptop.  That is what I had to get 
> for
> my VWs and it is called VAG-COM.  The capability/flexibility afforded by 
> this
> set up is amazing but it isn't cheap - yet.  Certainly cheaper than a big
> brand specific diagnostic machine that garages had to buy in the "olden" 
> days.
> To combat the eventuality of a $20 cable and bootlegged software, they are
> placing a chip in the cable and the full-capability, supported software 
> looks
> for the chip before it will work.  I guess it is simply too much to ask 
> for
> all car manufacturers to use common or open source programming for their
> products.  With no incentive, why would they? MB
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From: "Randall" <[email-masked]>
Date: Tue, 6 Nov 2012 07:32:26 -0800

> placing a chip in the cable and the full-capability, 
> supported software looks
> for the chip before it will work.

Actually, that chip is a fairly sophisticated microprocessor, with the
integrated hardware controllers required to talk to CAN bus (OBD-II) on one
side, and USB bus on the other.  They are very different interfaces; and CAN
in particular is a very odd network protocol.

The ones sold to garage mechanics are also quite limited in functionality.
We just bought some more of the "good stuff" at work, and they were nearly
$2000 each just for the hardware and software library to communicate with
it.

>   I guess it is simply too 
> much to ask for
> products.  With no incentive, why would they?

There are in fact powerful disincentives not to.  There is a great deal of
money spent on developing that software and it changes pretty much
constantly.  Giving away source code that cost literally tens or even
hundreds of millions of dollars to develop and can benefit only one's
competitors just isn't going to happen.

But you are quite right, those diagnostic addresses are only the tip of the
iceberg for what is actually going on inside.  I spend a good deal of my
professional life writing CAN bus code; and diagnostic addresses are just
something that gets stuck on afterwards, to help troubleshoot problems in
the field.  That's pretty much the way it has to be, since a DA can only be
updated at 10 Hz or so, but practically any control loop (ignition, fuel,
ABS, etc) has to run much faster.  We run up to 1 kHz in software, faster
loops are done in (custom) hardware.

-- Randall  

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