Operation Manual

<CR> [ repeat the last command ]
Sending a single carriage return character causes
the ELM327 to repeat the last command that it
performed. This is typically used when you wish to
obtain updates to a value at the fastest possible rate -
for example, you may send 01 0C to obtain the engine
rpm, then send only a carriage return character each
time you wish to receive an update.
AL [ Allow Long messages ]
The standard OBDII protocols restrict the number
of data bytes in a message to seven, which the
ELM327 normally does as well (for both send and
receive). If AL is selected, the ELM327 will allow long
sends (eight data bytes) and long receives (unlimited
in number). The default is AL off (and NL selected).
AMC [ display Activity Monitor Count ]
The Activity Monitor uses a counter to determine
just how active the ELM327's OBD inputs are. Every
time that activity is detected, this counter is reset,
while if there is no activity, the count goes up (every
0.655 seconds). This count then represents the time
since activity was last detected, and may be useful
when writing your own logic based on OBD activity.
The counter will not increment past FF (internal logic
stops it there), and stays at 00 while monitoring.
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AT Command Summary (continued)
CAN Specific Commands (continued)
D0, D1 display of the DLC off*, or on
FC SM h Flow Control, Set the Mode to h
FC SH hhh FC, Set the Header to hhh
FC SH hhhhhhhh Set the Header to hhhhhhhh
FC SD [1 - 5 bytes] FC, Set Data to [...]
PB xx yy Protocol B options and baud rate
RTR send an RTR message
V0, V1 use of Variable DLC off*, or on
J1939 CAN Specific Commands (protocols A to C)
DM1 monitor for DM1 messages
JE use J1939 Elm data format*
JHF0, JHF1 Header Formatting off, or on*
JS use J1939 SAE data format
JTM1 set Timer Multiplier to 1*
JTM5 set Timer Multiplier to 5
MP hhhh Monitor for PGN 0hhhh
MP hhhh n “ “ and get n messages
MP hhhhhh Monitor for PGN hhhhhh
MP hhhhhh n “ “ and get n messages
AT Command Descriptions
The following describes each AT Command that the
current version of the ELM327 supports:
AMT hh [ set the Act Mon Timeout to hh ]
When the Activity Monitor Count (ie time) exceeds
a certain threshold, the ELM327 decides that there is
no OBD activity. It might then give an ACT ALERT
message or switch to Low Power operation, depending
on how the bits of PP 0F are set. The threshold setting
is determined by either PP 0F bit 4, or by the AT AMT
value, should you provide it. The actual time to alarm
will be (hh+1) x 0.65536 seconds. Note that a value of
00 is accepted for AMT, but is used to block all Activity
Monitor outputs.
AR [ Automatically set the Receive address ]
Responses from the vehicle will be acknowledged
and displayed by the ELM327, if the internally stored
receive address matches the address that the
message is being sent to. With the auto receive mode
in effect, the value used for the receive address will be
chosen based on the current header bytes, and will
automatically be updated whenever the header bytes
are changed.
The value that is used for the receive address is
determined based on such things as the contents of
the first header byte, and whether the message uses
physical addressing, functional addressing, or if the
user has set a value with the SR or RA commands.
Auto Receive is turned on by default, and is not
used by the J1939 protocol.