[Shop-talk] OBD/can/whatever scan issue.

[Todd Walke]

Randall wrote:

>Actually required by law in the US, since 1996 model year.  But CAN is 
>only a physical and data link layer, similar in concept to 10Base-T and 
>Ethernet.  There are lots of layers that run on top of it (think TCP/IP 
>and HTML) as well as lots of possible variations at each level.
>
>For example, my 95 Buick uses a CAN bus, but practically none of the 
>scanners support it because it is still OBD-I and uses different (GM 
>proprietary) addresses and message types than specified in OBD-II.
>
>My understanding is that OBD-II was supplanted in 2008 with a newer 
>protocol, called ISO 15765-4.  But I've not had to dig into it yet.

         I use a product called VCDS, which is written specifically to 
interface with VW cars.  Someone on a VW forum asked the maker of VCDS if 
their interfaces would work with other models of cars.  Here is the reply 
from the company owner with some info on the various protocols used for 
OBDII interfaces.

=================

No vehicles except those built by the VW/Audi Group are "Supported"; i.e. 
we don't guarantee the generic OBD-II functionality to work on any car not 
made by VAG.

That said, there are four different hardware protocols for generic OBD-II. 
These are:

1) ISO 9141 "K-Line". This uses pin 7 on the diagnostic port for half 
duplex, asynchronous, RS-like signalling. This is used by most imported 
cars between 1996 and 2004, as well as most Chrysler products from 1996 - 
2000. Since VW/Audi Group cars also use K-Line for their native 
diagnostics, most of our interfaces (except the Micro-CAN) can (in 
principle) handle this.

2) SAE J1850-VPW. This uses pin 2 on the diagnostic port for a "Variable 
Pulse Width" type of signalling, and was used by most GM products as well 
as some Toyotas from 1996-2004, and most Chrysler products from 2000-2004. 
None of our current interfaces have the hardware require to work with this.

3) SAE J1850-PWM. This uses pins 2 and 9 on the diagnostic port for a 
"Pulse Width Modulated" type of signalling and was used by most Ford 
products from 1996-2004. None of our current interfaces have the hardware 
require to work with this.

4) ISO 15765 "CAN". This uses pins 6 and 14 for Controller Area Network 
type signalling. This started replacing all the other protocols in 2004. 
However, the other protocols were still allowed through 2007. As of model 
year 2008, all cars sold in the US market are required to use CAN for 
generic OBD-II. All of our CAN-capable interfaces can (in principle) handle 
this.

Since we specialize in VW/Audi Group cars and don't sell our products as a 
generic OBD-II solution for other brands, we have not even attempted to 
compile a detailed list of which models of cars require which hardware 
protocol. VW/Audi Group cars only use 1) and 4). With other cars, your best 
bet is to look at which pins are populated on the OBD-II socket in the car. 
If they have contacts at 2 or 2 and 9, chances are VCDS won't work. If they 
have contacts at 7 or 6 and 14, VCDS might, at least in principle work.



Todd
Seattle,WA
'86 GTI, Red of course. (exciting racey car) 276,000 miles
'01 Golf TDI, silver.   (new work car)       456,000 miles
'87 Golf, Polar Silver. (retired work car)   654,000 miles <- Gone to a new 
home :(
http://www.pureluckdesign.com <-Ferrari & VW stuff