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#1: OBD-II simulator

Posted on 2005-03-06 00:38:19 by DNW

I'm building an OBD-II code scanner for a University project, and I'm at
the point where I'm ready to test it. Although I have designed several
precautionary measures, I am a bit nervous about plugging it into cars
before running some more basic tests. The question is, then, how can I
simulate raw J1962 output of known error codes? I am using the ELM 32x
series to convert to the standard RS-232 signals.

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#2: Re: OBD-II simulator

Posted on 2005-03-06 04:32:01 by JazzMan

DNW wrote:
>
> I'm building an OBD-II code scanner for a University project, and I'm at
> the point where I'm ready to test it. Although I have designed several
> precautionary measures, I am a bit nervous about plugging it into cars
> before running some more basic tests. The question is, then, how can I
> simulate raw J1962 output of known error codes? I am using the ELM 32x
> series to convert to the standard RS-232 signals.

Take a good 12V battery and the scanner to the junkyard and
power up a wrecked car that hasn't been stripped yet. You
should get plenty of error codes. :)

JazzMan
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Curse those darned bulk e-mailers!
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live under the laws of justice and mercy." - Wendell Berry
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#3: Re: OBD-II simulator

Posted on 2005-03-07 10:55:10 by Ted Mittelstaedt

&quot;DNW&quot; &lt;<a href="mailto:teslacoil&#64;ameritech.net" target="_blank">teslacoil&#64;ameritech.net</a>&gt; wrote in message
news:LprWd.16781$<a href="mailto:hU7.14430&#64;newssvr33.news.prodigy.com..." target="_blank">hU7.14430&#64;newssvr33.news.prodigy.com...</a>
&gt; I'm building an OBD-II code scanner for a University project, and I'm at
&gt; the point where I'm ready to test it. Although I have designed several
&gt; precautionary measures, I am a bit nervous about plugging it into cars
&gt; before running some more basic tests.

I hope you have disassembled at least one commercial OBD-II code
scanners to see what precautionary measures they have taken.

Ted

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#4: Re: OBD-II simulator

Posted on 2005-03-07 16:05:58 by Joey Oravec

&quot;DNW&quot; &lt;<a href="mailto:teslacoil&#64;ameritech.net" target="_blank">teslacoil&#64;ameritech.net</a>&gt; wrote in message
news:LprWd.16781$<a href="mailto:hU7.14430&#64;newssvr33.news.prodigy.com..." target="_blank">hU7.14430&#64;newssvr33.news.prodigy.com...</a>
&gt; I'm building an OBD-II code scanner for a University project, and I'm at
&gt; the point where I'm ready to test it. Although I have designed several
&gt; precautionary measures, I am a bit nervous about plugging it into cars
&gt; before running some more basic tests. The question is, then, how can I
&gt; simulate raw J1962 output of known error codes? I am using the ELM 32x
&gt; series to convert to the standard RS-232 signals.

It is good to be nervous -- DrewTech optically isolates the host interface
from the vehicle by 1500V, because a running car is really a harsh
environment!

I've written a simple PassThru API (SAE J2534) based OBD-II simulator in
LabVIEW for DrewTech's CarDAQ2534. Unfortunately the ELM is a hobbyist box
and its driver is not PassThru API compliant. If you have a CarDAQ2534 and
LabVIEW available, I could probably send you my simulation program.

The OBD-II (SAE J1979) document describes the protocol for commands and
responses. My program basically decodes the message header, identifies the
mode (command), and transmits a properly formatted response to the tester.
The basic process to read DTCs is:

1. Establish a logical communication channel with the ECU (any
initialization necessary per-protocol)
2. Use mode 01 pid 01 to report MIL status, and # of DTCs
3. If (# DTCs &gt; 0), then use mode 03 to report the DTC values
4. Optionally use mode 04 to clear set DTCs

All of these processes are defined in the SAE document. Check our website
www.drewtech.com for more information about CarDAQ and vehicle communication
in general. If you're a CarDAQ user, drop me an email and I'll see what I
can do about sending some sample source code for OBD-II requests and
responses.

-joey

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