<s>
Society	O
of	O
Automotive	O
Engineers	O
standard	O
SAE	B-Application
J1939	I-Application
is	O
the	O
vehicle	B-Architecture
bus	I-Architecture
recommended	O
practice	O
used	O
for	O
communication	O
and	O
diagnostics	O
among	O
vehicle	O
components	O
.	O
</s>
<s>
SAE	B-Application
J1939	I-Application
is	O
used	O
in	O
the	O
commercial	O
vehicle	O
area	O
for	O
connection	O
and	O
communication	O
throughout	O
the	O
vehicle	O
,	O
with	O
the	O
physical	O
layer	O
defined	O
in	O
ISO	O
11898	O
.	O
</s>
<s>
Originally	O
,	O
Controller	B-Protocol
Area	I-Protocol
Network	I-Protocol
(	O
CAN	O
)	O
was	O
not	O
mentioned	O
in	O
J1939	B-Application
,	O
which	O
covered	O
cars	O
and	O
tractor-trailer	O
rigs	O
,	O
and	O
with	O
some	O
dual	O
and	O
triple	O
use	O
8-bit	O
addresses	O
assigned	O
by	O
the	O
SAE	B-Application
J1939	I-Application
board	O
.	O
</s>
<s>
CAN	O
was	O
not	O
originally	O
free	O
,	O
but	O
its	O
instruction	O
set	O
did	O
fit	O
in	O
the	O
custom	O
instruction	O
format	O
of	O
J1939	B-Application
.	O
</s>
<s>
Since	O
then	O
,	O
CAN	O
has	O
been	O
included	O
,	O
the	O
chipset	O
for	O
J1939	B-Application
has	O
been	O
clocked	O
faster	O
,	O
and	O
16-bit	O
addresses	O
(	O
PGN	O
)	O
have	O
replaced	O
8-bit	O
addresses	O
.	O
</s>
<s>
J1939	B-Application
,	O
ISO	B-Protocol
11783	I-Protocol
and	O
NMEA	O
2000	O
all	O
share	O
the	O
same	O
high	O
level	O
protocol	O
.	O
</s>
<s>
SAE	B-Application
J1939	I-Application
can	O
be	O
considered	O
the	O
replacement	O
for	O
the	O
older	O
SAE	O
J1708	O
and	O
SAE	O
J1587	O
specifications	O
.	O
</s>
<s>
SAE	B-Application
J1939	I-Application
defines	O
five	O
layers	O
in	O
the	O
seven-layer	O
OSI	O
network	O
model	O
,	O
and	O
this	O
includes	O
the	O
Controller	B-Protocol
Area	I-Protocol
Network	I-Protocol
(	O
CAN	O
)	O
ISO	O
11898	O
specification	O
(	O
using	O
only	O
the	O
29-bit/	O
"	O
extended	O
"	O
identifier	O
)	O
for	O
the	O
physical	O
and	O
data-link	O
layers	O
.	O
</s>
<s>
Under	O
J1939/11	O
and	O
J1939/15	O
,	O
the	O
data	O
rate	O
is	O
specified	O
as	O
250	O
kbit/s	O
,	O
with	O
J1939/14	O
specifying	O
500	O
kbit/s	O
.	O
</s>
<s>
All	O
J1939	B-Application
packets	O
,	O
except	O
for	O
the	O
request	O
packet	O
,	O
contain	O
eight	O
bytes	O
of	O
data	O
and	O
a	O
standard	O
header	O
which	O
contains	O
an	O
index	O
called	O
Parameter	O
Group	O
Number	O
(	O
PGN	O
)	O
,	O
which	O
is	O
embedded	O
in	O
the	O
message	O
's	O
29-bit	O
identifier	O
.	O
</s>
<s>
J1939	B-Application
attempts	O
to	O
define	O
standard	O
PGNs	O
to	O
encompass	O
a	O
wide	O
range	O
of	O
automotive	O
,	O
agricultural	O
,	O
marine	O
and	O
off-road	O
vehicle	O
purposes	O
.	O
</s>
<s>
SAE	B-Application
J1939	I-Application
has	O
been	O
adopted	O
widely	O
by	O
diesel	O
engine	O
manufacturers	O
.	O
</s>
<s>
One	O
driving	O
force	O
behind	O
this	O
is	O
the	O
increasing	O
adoption	O
of	O
the	O
engine	O
Electronic	B-Device
Control	I-Device
Unit	I-Device
(	O
ECU	O
)	O
,	O
which	O
provides	O
one	O
method	O
of	O
controlling	O
exhaust	O
gas	O
emissions	O
within	O
US	O
and	O
European	O
standards	O
.	O
</s>
<s>
The	O
telematics	O
data	O
is	O
used	O
(	O
via	O
Fleet	O
Telematics	O
Systems	O
)	O
by	O
Fleet	B-Application
Management	I-Application
Systems	I-Application
to	O
let	O
fleet	O
operators	O
keep	O
track	O
of	O
vehicle	O
and	O
driver	O
performance	O
,	O
such	O
as	O
fuel	O
consumption	O
,	O
safety	O
events	O
,	O
and	O
repair	O
time	O
.	O
</s>
<s>
Consequently	O
,	O
SAE	B-Application
J1939	I-Application
can	O
now	O
be	O
found	O
in	O
a	O
range	O
of	O
diesel-powered	O
applications	O
:	O
vehicles	O
(	O
on	O
-	O
and	O
off-road	O
and	O
rail	O
)	O
,	O
marine	O
propulsion	O
,	O
power	O
generation	O
and	O
industrial	O
pumping	O
.	O
</s>
