Searching \ for '[OT] Diagnostic plug' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/index.htm?key=diagnostic+plug
Search entire site for: 'Diagnostic plug'.

Exact match. Not showing close matches.
PICList Thread
'[OT] Diagnostic plug'
2004\10\18@034806 by Attila Muhi

flavicon
face
Hi list,


I know, this is off topic, but I have tried Google, and have no idea where to search for this...


I need the pinout for the diagnostic plug in my car. I have some trouble with the ABS brakes, and want to retrieve the fault code. As far as I know a slow pulse train should be available somewhere in that plug.... Probably I won't need a pic to read the pulse train :-) , just a led or a scope. But which pin, and how do I interpret the code ?

This seems to be a well hidden secret. !!!    Btw, it's a MB diesel, year 1994.


Regards

Attila - SM4RAN
______________________________________________________

Gratis visitkort - klicka här !
Allt inom e-handel! http://www.torget.se




_______________________________________________
http://www.piclist.com
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

2004\10\18@095741 by Dave VanHorn

flavicon
face
At 02:54 AM 10/18/2004, Attila Muhi wrote:

>Hi list,
>
>
>I know, this is off topic, but I have tried Google, and have no idea where
>to search for this...
>
>
>I need the pinout for the diagnostic plug in my car. I have some trouble
>with the ABS brakes, and want to retrieve the fault code. As far as I know
>a slow pulse train should be available somewhere in that plug.... Probably
>I won't need a pic to read the pulse train :-) , just a led or a scope.
>But which pin, and how do I interpret the code ?
>
>This seems to be a well hidden secret. !!!    Btw, it's a MB diesel, year
>1994.

This will be hard to find, it's OBD diagnostics, and the implementation
varies according to manufacturer.  After 1996, there's OBD-II which tells
you more but still varies per manufacturer.


_______________________________________________
http://www.piclist.com
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

2004\10\18@123120 by Peter Johansson

flavicon
face
Attila Muhi writes:

> I know, this is off topic, but I have tried Google, and have no idea where to search for this...
>
> I need the pinout for the diagnostic plug in my car. I have some
> trouble with the ABS brakes, and want to retrieve the fault code. As
> far as I know a slow pulse train should be available somewhere in
> that plug.... Probably I won't need a pic to read the pulse train
> :-) , just a led or a scope. But which pin, and how do I interpret
> the code ?
>
> This seems to be a well hidden secret. !!!  Btw, it's a MB diesel,
> year 1994.

This is one of the current scams in the auto industry.  The auto
manufacturers are keeping their diagnostic codes secret so (1) they
can profit by selling disgnostic hardware and software (2) they can
help their dealers by only supplying the dealers with the tools
required to disgnose problems in the car.

There are some 3rd party companies that reverse engineer the codes,
but even their products (hardware and software updates) are rather
expensive.  Many auto shops will charge $50-$100 just to hook your car
up to the computer and give you a reading!  Already gone are the days
of the "free estimate" when the computers are involved.

I believe there are actually several lawsuits regarding this.  I have
a recollection of one group suing the automakers to make their
disgnostic codes public, and I wouldn't be surprised if the auto
companies are using the DMCA to shut down the makers of 3rd-party
diagnostic gear.

That said, there may be a simple solution.  The "Auto Zone" chain in
the US has the diagnostic tools and software for many automobiles, and
they will give you a *free* diagnostic report.  However, their tools
are a bit on the basic side.  I was diagnosing a "check engine" light
problem that I was almost certain was an oxygen sensor fault.  When I
plugged into the Auto Zone computer, it did indeed confirm that the
oxygen sensor was at fault, but the software could not tell me which
of the two oxygen sensors had failed.  At $50 for one sensor and $90
for the other, it's no small matter to simply replace both!  Further
investigation revealed that the problem was not with either sensor,
but that one of the wires to sensor had chaffed through midway between
the wiring harness and sensor itself.

-p.
_______________________________________________
http://www.piclist.com
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

2004\10\18@125425 by Dave VanHorn

flavicon
face

I got the "auto-Enginuity" scanner, which works on everything, and talks to
my PC, and the palm-pilot (with serial port!)

Works great on all makes I've tried it on, ford, buick, chevy..

_______________________________________________
http://www.piclist.com
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

2004\10\18@135604 by Bob Blick

face picon face
> I need the pinout for the diagnostic plug in my car. I have some trouble
> with the ABS brakes, and want to retrieve the fault code. As far as I know
> a slow pulse train should be available somewhere in that plug.... Probably
> I won't need a pic to read the pulse train :-) , just a led or a scope.
> But which pin, and how do I interpret the code ?
> This seems to be a well hidden secret. !!!    Btw, it's a MB diesel, year
> 1994.

They are secrets, to lock you to the dealership for repairs. Even OBD-II
does not include ABS as part of the standard, it is manufacturer-specific.

However, diagnostic info is not always accurate. My wife's car presented
the error code "EGR vacuum valve solenoid has high resistance". Although
it seemed to function OK, I assumed it had an intermittent open, so I
replaced it and reset - same trouble code came back. I tested everything,
the valve functions in the car just as it should. I disassembled the
engine control unit, and looked at the circuitry that drives the EGR
vacuum solenoid - there was no way it could detect the current, it was
just a Darlington to ground, no voltage sensing or emitter resistor. The
positive feed was to a common bus with other outputs. A friend in the
industry suggested that the codes often are indirect and further down a
diagnostic flow chart, and as such, are not always accurate. He said that
more likely the ECU expects some change in engine vacuum or oxygen sensor
output when it triggers the EGR valve, and it wasn't seeing it. I finally
tracked it down to a stuck mechanical advance in the distributor.

So, my opinion of onboard diagnostics - not so good. Quite often the
result is a wild goose chase.

Cheerful regards,

Bob



_______________________________________________
http://www.piclist.com
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

2004\10\18@154509 by Steve Ruse

flavicon
face
In my experience the DTCs can be pretty helpful...I do have a fair amount of
experience but only with GM vehicles.  Others might not be so easy. Usually
when I determine what the code is, it makes it MUCH easier to track down the
problem. As for looking at the pulse train, it won't be quite that easy,
definately not with an LED, unless you can see pulses at 8192 baud. :) A scope
won't make it much easier, as the pulse train is a serial stream of data,
basically one byte of useful data (RPM, temperatures, sensor voltages, trouble
codes, etc.) every four or five bytes if I remember correctly.  Your best bet
might be to log a few seconds of the datastream through a serial port, then try
to find the datastream documentation and decode it. I could help you if it was
GM, but I don't know where to point your for an MB. It does help that it is a
'94 though...

ALSO, on many (most?) vehicles, the ABS computer is a completely separate device
from the drivetrain control module. Talking to the PCM may or may not give you
any useful data on your ABS system.

FYI, many auto parts stores (Autozone if you have them in your area) will read
the code & give you trouble codes for free, because they want you to buy their
parts. Mechanics and dealers will charge from $25 to $100+ for the same
information...

HTH,

Steve Ruse

Quoting Bob Blick <spam_OUTbblickTakeThisOuTspamsonic.net>:

{Quote hidden}

_______________________________________________
http://www.piclist.com
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

2004\10\18@171847 by SHands

flavicon
face
I'm not too sure about the US market - but over here in the UK, we've
got a range of books made by Haynes that disassemble all makes/models of
cars, reassemble them, and then write books telling the readers how to
do it and supply technical information along the way.

Personally, I've got a Ford Mondeo and thought several times about
dabbling in making an interface to talk to the ECU - given that the guys
at Haynes make it easy by giving pin-outs for the DLC connector (correct
acronym?) AND schematics for the ECU itself!

Having a quick search around to see what is already out there with
regards to pre-built diagnostic tools - I've found this interesting
interface which allows you to seemingly read fault codes/live data via a
serial link:

http://www.onboarddiagnostics.co.uk/interface/index.htm

Hmm. I wonder what that little black box is hiding, (coming back to the
list - I wonder if it contains a PIC?! It's interesting to see which
manufactures make use of our little friends!! ;)


Stuart


{Original Message removed}

2004\10\18@183820 by Bob Blick

face picon face
> In my experience the DTCs can be pretty helpful...I do have a fair amount
> of
> experience but only with GM vehicles.

Unfortunately, it was a GM vehicle, and the trouble code was less than
worthless, and caused an unnecessary repair to be done :(

I guess that's the point I was thinking about, but didn't make. The
trouble codes frequently lead mechanics to replace parts, even if that
isn't the problem, and they get away with it, because "the computer told
them to", and the customer pays.

Cheerful regards,

Bob


____________________________________________

2004\10\19@040708 by hael Rigby-Jones

picon face


>-----Original Message-----
>From: .....piclist-bouncesKILLspamspam@spam@MIT.EDU [piclist-bouncesspamKILLspamMIT.EDU]
>On Behalf Of Dave VanHorn
>Sent: 18 October 2004 17:55
>To: Microcontroller discussion list - Public.; Microcontroller
>discussion list - Public.
>Subject: Re: [OT] Diagnostic plug
>
>
>
>I got the "auto-Enginuity" scanner, which works on everything,
>and talks to
>my PC, and the palm-pilot (with serial port!)
>
>Works great on all makes I've tried it on, ford, buick, chevy..

I imagine it works great on anything that is ODBII compatible?  In Europe
the EODB standard is used, but has not been in use for very long (2001 for
petrol, 2003 for Diesel engined cars), so the number of cars a single scan
tool will work on is pretty limited at the moment.

Mike

=======================================================================
This e-mail is intended for the person it is addressed to only. The
information contained in it may be confidential and/or protected by
law. If you are not the intended recipient of this message, you must
not make any use of this information, or copy or show it to any
person. Please contact us immediately to tell us that you have
received this e-mail, and return the original to us. Any use,
forwarding, printing or copying of this message is strictly prohibited.
No part of this message can be considered a request for goods or
services.
=======================================================================
____________________________________________

2004\10\19@041117 by hael Rigby-Jones

picon face


>-----Original Message-----
>From: .....piclist-bouncesKILLspamspam.....mit.edu [EraseMEpiclist-bouncesspam_OUTspamTakeThisOuTmit.edu]
>On Behalf Of Bob Blick
>Sent: 18 October 2004 18:56
>To: Microcontroller discussion list - Public.
>Subject: Re: [OT] Diagnostic plug
>
>So, my opinion of onboard diagnostics - not so good. Quite
>often the result is a wild goose chase.

Like any diagnostic tool, the result requires interpretation.  The
diagnostic codes are usefull, but as you have found, does not make
experienced engineers redundant.  Unfortunately many garages do not
understand this, and take diagnostic codes as gospel, replacing sensors that
are operating perfectly well and charging the customer for their lack of
experience.

Mike

=======================================================================
This e-mail is intended for the person it is addressed to only. The
information contained in it may be confidential and/or protected by
law. If you are not the intended recipient of this message, you must
not make any use of this information, or copy or show it to any
person. Please contact us immediately to tell us that you have
received this e-mail, and return the original to us. Any use,
forwarding, printing or copying of this message is strictly prohibited.
No part of this message can be considered a request for goods or
services.
=======================================================================
____________________________________________

2004\10\19@044238 by Attila Muhi

flavicon
face
It seems to be just as complicated as I thought it was :-)

At first I called the MB representative to ask for advice, they just said: "We can trace the fault if you come to us, there's no other way to go..." I could hear their big smiles along the phone line, guess they were thinking of the bill I would receive....

I think I should measure the resistance of the sensors first.... And the attack the diagnostic plug with a scope, just to see what's inside.. But there are 16 pins ....


I found a forum btw, someone posted an address here, I'll search that one as well.....


cheers

Attila - SM4RAN
______________________________________________________

Gratis visitkort - klicka här !
Allt inom e-handel! http://www.torget.se


-----Ursprungligt meddelande-----
Från: Dave VanHorn <dvanhornspamspam_OUTdvanhorn.org>
Till: Microcontroller discussion list - Public. <@spam@piclistKILLspamspammit.edu>; Microcontroller discussion list - Public. <KILLspampiclistKILLspamspammit.edu>
Datum: den 18 oktober 2004 19:34
Ämne: Re: [OT] Diagnostic plug


{Quote hidden}

___________________________________________

2004\10\19@124005 by Bob Blick

face picon face

> Like any diagnostic tool, the result requires interpretation.  The
> diagnostic codes are usefull, but as you have found, does not make
> experienced engineers redundant.  Unfortunately many garages do not
> understand this, and take diagnostic codes as gospel, replacing sensors
> that
> are operating perfectly well and charging the customer for their lack of
> experience.

I think it's less benign than that - yes, they allow themselves to become
lazy, but they make money on parts, and use the tool as a way to fleece
the customers. "The computer said the part was bad, so the part was bad".

My motto is, if I can't fix it myself, I'll buy a new car. No garages for me.

Cheerful regards,

Bob




____________________________________________

2004\10\19@154046 by Attila Muhi

flavicon
face




{Quote hidden}

A newer car = more black boxes...     :-)


Attila - SM4RAN



>
>
>
>
>_____________________________________________

2004\10\20@200255 by Dave Lag

picon face
But sometimes they work as advertised. I borrowed a tool plugged it in to my GM
and got boatload of codes, one of which was "throttle stuck".
True enough the actuating pin was broken off. Fixing that cleared ALL codes.
Maybe there is logic to finding the furthest  "upstream" code?

The amazing part is that the car ran reasonably well, just using the other
sensors
MAF O2 etc....

Dave

At 12:40 PM 10/19/04, you wrote:

{Quote hidden}

____________________________________________

2004\10\22@050820 by Attila Muhi

flavicon
face
Here we go again....

I gave up on the diagnostic plug, took my Fluke and noticed that the resistance of the rear abs sensor was several megaohms...

Hmm, maybe I should scope/log all pins in the plug, and compare before and after replacing that sensor...


Does anyone of you know if there's a logging freeware somwhere ?  Building an i/f or level converter for the serial port is no problem ....


Regards, and thanks for all replies



Attila - SM4RAN




____________________________________________

2004\10\23@070316 by SHands

flavicon
face
I can't remember who posted the question about free software to read
diag codes - but I've found one, (beit very simple). They offer the C
source code - so it shouldn't be too hard to mod your serial i/face to
suit.

Check http://www.scantool.net for details and
http://www.scantool.net/software/scantool.net/index.shtml#download to
download it.

Interestingly, this is only designed for use with any one of their own
interfaces, (one random pictured here:
http://www.scantool.net/products/elmscan_iso.htm). I wonder what that
"ELM323" sticker is hiding? A PIC maybe? Lol

Hope this helps for your quest with the ABS fault...

Stuart


-----Original Message-----
From: RemoveMEpiclist-bouncesTakeThisOuTspamMIT.EDU [spamBeGonepiclist-bouncesspamBeGonespamMIT.EDU] On Behalf
Of Dave VanHorn
Sent: 18 October 2004 14:58
To: Microcontroller discussion list - Public.; Microcontroller
discussion list - Public.
Subject: Re: [OT] Diagnostic plug

...
etc

____________________________________________

More... (looser matching)
- Last day of these posts
- In 2004 , 2005 only
- Today
- New search...