ELM327P datasheet(72/76 Pages) ELM

72 / 76 page

Error Messages and Alerts

This is the standard response for a misunderstood

command received on the RS232 input. Usually it is

due to a typing mistake, but it can also occur if you try

to do something that is not appropriate (eg. trying to do

an AT FI command if you are not set for protocol 5).

ACT ALERT

This message occurs as a warning that there has

been no RS232 activity (ie commands or messages

received) for either 4 or 19 minutes (depends on the

setting of PP 0E bit 4). It means that the IC will be

initiating a switch to the Low Power (standby) mode of

operation in 1 minute, unless RS232 characters are

received during that time. This warning is not provided

if PP 0E bit 3 is 0.

BUFFER FULL

The ELM327 provides a 256 byte internal RS232

transmit buffer so that OBD messages can be received

quickly, stored, and sent to the computer at a more

constant rate. Occasionally (particularly with CAN

systems) the buffer will fill at a faster rate than it is

being emptied by the PC. Eventually it may become

full, and no more data can be stored (it is lost).

If you are receiving BUFFER FULL messages,

and you are using a lower baud data rate, give serious

consideration to changing your data rate to something

higher. If you still receive BUFFER FULL messages

after that, you might consider turning the headers and

maybe the spaces off (with AT H0, and AT S0), or

using the CAN filtering commands (AT CRA, CM and

CF) to reduce the amount of data being sent.

BUS BUSY

This occurs when the ELM327 tries to send a

message, or to initialize the bus, and detects too much

activity to do so (it needs a pause in activity in order to

insert the message). Although this could be because

the bus was in fact very busy, it is almost always due

to a wiring problem that is giving a continuously active

input. If this is an initial trial with your new ELM327

circuit, then check all of the voltage levels at the

offending OBD input, as this error is very likely due to

a wiring problem (see our ‘AN02 - ELM327 Circuit

Construction’ for some typical voltages).

BUS ERROR

A generic problem has occurred. This is most

often from an invalid signal being detected on the bus

(for example, a pulse that is longer than a valid Break

signal), but usually is from a wiring error. Note that

some vehicles may generate long pulses as part of

their startup process, so you may see this message as

part of a normal vehicle startup while ‘monitoring all.’

CAN ERROR

The CAN system had difficulty initializing, sending,

or receiving. Often this is simply from not being

connected to a CAN system when you attempt to send

a message, but it may be because you have set the

system to an incorrect protocol, or to a baud rate that

does not match the actual data rate. As with BUS

ERRORs, the CAN ERROR might also be the result of

a wiring problem, so if this is the first time using your

ELM327 circuit, review all of your CAN interface

circuitry before proceeding.

DATA ERROR

There was a response from the vehicle, but the

information was incorrect or could not be recovered.

<DATA ERROR

There was an error in the line that this points to,

either from an incorrect checksum, or a problem with

the format of the message (the ELM327 still shows

you what it received). There could have been a noise

burst which interfered, possibly a circuit problem, or

perhaps you have the CAN Auto Formatting (CAF) on

and you are looking at a system that is not of the

ISO 15765-4 format. Try resending the command

again – if it was a noise burst, it may be received

correctly the second time.

The following shows what the ELM327 will send to

warn you of a condition or a problem. Some of these

messages do not appear if using the automatic search

for a protocol, or if the Programmable Parameter bits

disable them.

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