I
A Comprehensible Guide to J1939
Copperhill Media Corporation
http://www.copperhillmedia.com
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A Comprehensible Guide to J1939
By Wilfried Voss
Published by
Copperhill Media Corporation
158 Log Plain Road
Greenfield, MA 01301
Copyright © 2008 by Copperhill Media Corporation, Greenfield, Massachusetts
No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or
by any means, electronic, mechanical, photocopying, recording, scanning or otherwise, except as
permitted under Sections 107 or 108 of the 1976 United States Copyright Act, without the prior written
permission of the Publisher.
ISBN: 978-0-9765116-3-2
Printed in the United States of America
Limit of Liability/Disclaimer of Warranty
While the publisher and author have used their best efforts in preparing this book, they make no
representations or warranties with respect to the accuracy or completeness of the contents of this book
and specifically disclaim any implied warranties or merchantability or fitness for a particular purpose. No
warranty may be created or extended by sales representatives or written sales materials. The advice and
strategies contained herein may not be suitable for your situation. You should consult with a professional
where appropriate. Neither the publisher nor author shall be liable for any loss or profit or any other
commercial damages, including but not limited to special, incidental, consequential, or other damages.
158 Log Plain Road
Greenfield, MA 01301
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About this book
After writing “A Comprehensible Guide to Controller Area Network”, documenting the SAE
J1939 standard seemed to be a logical choice when it came to investigating CAN based higher
layer protocols. As I have learned from a number or professionals in the CAN industry, J1939
is still gaining enormous popularity, even though it is already in business for some years.
However, the quality and availability of documentation on J1939 is in utter contrast to its
popularity.
According to Wikipedia, the biggest multilingual free-content encyclopedia on the Internet,
"SAE J1939 is the vehicle bus standard used for communication and diagnostics among vehicle
components, originally by the car and heavy duty truck industry in the United States." Beyond
that statement there is only few information to find on J1939 and the same is true for the
entire World Wide Web.
The SAE (Society of Automotive Engineers), like many standardization organizations, is
keeping a close lock on their written works and profound information on their web site is
sparse. Downloading the J1939 PDF documents comes with a hefty price tag, even for SAE
members who receive a discount not worth mentioning.
At the time when this book was released the only available and complete technical reference
on J1939 was provided by the SAE either as PDF downloads for a price tag of US$595.00
(Single-User, one-year subscription) or one could buy the complete SAE J1939 standard in one
colossal work of 1600+ pages for a mere US$310.00. Regular books dedicated to J1939 and
available for a reasonable price did not exist at the time when I started the research and, as
mentioned previously, valid references on the World Wide Web were extremely sparse.
Beyond the commercial aspects there is also the issue of educational value and readability of
these standards. Standards, like those developed for J1939, are not designed to educate or,
God forbid, entertain.
Standardization organizations seem to be the worst when it comes to providing
comprehensible and readable documentation of the products they are trying to promote, which
ironically creates revenues for technical writers who actually know their job.
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Despite the poor condition of the written standard, it was initially a pleasure to investigate the
J1939 protocol functions. SAE J1939 is a very ingeniously designed protocol that takes a
resourceful advantage of the CAN 29-Bit message identifier. Rather than relying on a myriad of
protocol functions, SAE J1939 uses predefined parameter tables, which keeps the actual
protocol on a comprehensible level. SAE J1939 is a prime example of good American
engineering according to the KISS principle (KISS = Keep It Simple, Stupid!), but it is
nevertheless at least as effective as, for instance, CANopen or DeviceNet.
I had originally contemplated to continue my “Comprehensible Guide” series with CANopen,
but was overwhelmed by the amount of information that I would need to compile, which also
indicates the effort it takes for the newcomer to get familiarized with the topic. SAE J1939 was
so much more fun to investigate (again, initially), because it seemed simple and straight-
forward. However, this conclusion can only be made after relentless digging through the
standards and, after repeated reading, finally understanding what the authors were trying to
convey to the reader.
This book is an attempt to create an enjoyable and readable J1939 reference for everybody.
The information provided in this book is, besides the SAE J1939 Standards Collection, based on
publicly available information such as, but not limited to web sites and printed literature as
well as contributions by engineers familiar with Controller Area Network and the J1939
protocol. The information in this book, while based on the J1939 standard, is not a
reproduction of any copyrighted SAE document.
Also, this book does not intend to replace the entire SAE J1939 Standards Collection, especially
since the standards SAE J1939 and SAE J1939/71 contain mainly data references which
account to more than 1000 pages of 8.5 x 11” in size. These data references are not part of
this book. The mere intention was to explain the standard in the sense of being a
comprehensible guide.
I also need to apologize in advance that the information in this book may seem to be repetitive
at times.
First of all, I always try to provide a generic overview of the topic covered in my books. This
will help people with a lesser technical background to understand the technology without
having to read all details.
