ELM329
AT Commands
Several parameters within the ELM329 can be
it was successfully completed.
adjusted in order to modify its behaviour. These do not
normally have to be changed before attempting to talk
to the vehicle, but occasionally the user may wish to
customize these settings – for example by turning the
character echo off, adjusting a timeout value, or
changing the header (ID) bytes. In order to do this,
internal ‘AT’ commands must be used.
Those familiar with PC modems will immediately
recognize AT commands as a standard way in which
modems are internally configured. The ELM329 uses
essentially the same method, always watching the
data sent by the PC, looking for messages that begin
with the character ‘A’ followed by the character ‘T’. If
found, the next characters will be interpreted as an
internal configuration or ‘AT’ command, and will be
executed upon receipt of a terminating carriage return
character. If the command is just a setting change, the
ELM329 will reply with the characters ‘OK’, to say that
Some of the commands require that numbers be
provided as arguments, in order to set the internal
values. These will always be hexadecimal numbers
which must generally be provided in pairs. The
hexadecimal conversion chart in the OBD Commands
section (page 26) may be helpful if you wish to
interpret the values. Also, one should be aware that for
the on/off types of commands, the second character is
the number 1 or the number 0, the universal terms for
on and off.
The remainder of this page, and the next page
following provide a summary of all of the commands
that the current version of the ELM329 recognizes. A
more complete description of each command begins
on page 11.
AT Command Summary
ELM329 Options
Programmable Parameters
<CR>
BRD hh
BRT hh
D
repeat the last command
try Baud Rate Divisor hh
set Baud Rate Timeout
set all to Defaults
PP xx OFF
PP FF OFF
PP xx ON
PP FF ON
disable Prog Parameter xx
all Prog Parameters disabled
enable Prog Parameter xx
all Prog Parameters enabled
E0, E1
I
Echo off, or on*
PP xx SV yy for PP xx, Set the Value to yy
print the version ID
PPS
print a PP Summary
L0, L1
LP
Linefeeds off, or on
Voltage Readings
CV dddd
CV 0000
go to low power mode
Memory off, or on
Calibrate the Voltage to dd.dd volts
restore CV value to factory setting
Read the input Voltage
M0, M1
RD
Read the stored Data
Save Data byte hh
RV
SD hh
WS
Warm Start (quick software reset)
reset all
Other
C0, C1
IGN
Z
Control Output off*, or on
read the IgnMon input level
read INput 1 level
@1
display the device description
display the device identifier
@2
IN1
@3 cccccccccccc store the @2 identifier
IN2
read INput 2 level
Note: Settings shown with an asterisk (*)
are the default values
ELM329DSB
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