ELM320(2003) 查看數據表（PDF） - Elm Electronics

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ELM320
(Rev.:2003)

OBD (PWM) to RS232 Interpreter

Elm Electronics 

ELM320

Resetting Trouble Codes

The ELM320 is quite capable of resetting

diagnostic trouble codes, as this only requires issuing

a mode 04 command. The consequences should

always be considered before sending it, however, as

more than the MIL (or ‘Check Engine’ lamp) will be

reset. In fact, issuing a mode 04 will:

- reset the number of trouble codes

- erase any diagnostic trouble codes

- erase any stored freeze frame data

- erase the DTC that initiated the freeze frame

- erase all oxygen sensor test data

- erase mode 06 and 07 test results

Clearing of all of this information is not unique to

the ELM320, as it occurs whenever a scan tool is used

to reset your codes. Understand that the loss of this

data could cause your car to run poorly for a short time

while the system recalibrates itself.

To avoid inadvertently erasing stored information,

the SAE specifies that scan tools must verify that a

mode 04 is intended (“Are you sure?”) before actually

sending it to the vehicle, as all trouble code

information is immediately lost when the mode is sent.

Recall, though, that the ELM320 does not monitor the

content of messages, so it will not know to ask for

confirmation of the mode request - this would have to

be the duty of a software interface if one is written.

As stated, to actually erase diagnostic trouble

codes, one need only issue a mode 04 command. A

response of 44 from the vehicle indicates that the

mode request has been carried out, the information

erased, and the MIL turned off. Some vehicles may

require a special condition to occur (the ignition on but

the engine not running, etc.) before it will respond to a

mode 04 command.

That is all there is to clearing the codes. Once

again, be very careful not to inadvertently issue an 04!

Error Messages

When hardware or data problems are

encountered, the ELM320 will respond with one of the

following short messages. Here is a brief description of

each…

BUS BUSY

The ELM320 tried to send the mode command or

request for about 0.5 seconds without success.

Messages are all assigned priorities, which allows

one message to take precedence over another.

More important things may have been going on, so

try re-issuing your request.

BUS ERROR

An attempt was made to send a message, and the

data bus voltage did not respond as expected. This

could be because of a circuit short or open, so check

all of your connections and try once more.

<DATA ERROR

The error check result (CRC byte) was not as

expected, indicating a data error in the line pointed

to (the ELM320 still shows you what it received).

There could have been a noise burst which

interfered, or a circuit problem. Try re-sending the

request.

NO DATA

There was no response obtained from the vehicle

before a timeout occurred. The mode requested may

not be supported, so the vehicle ignored you, or the

timeout value was too short, or possibly the ignition

key needs to be turned to ‘on’. Try issuing a 01 00

command to be sure that the vehicle is ready to

receive commands, and if that works, try adjusting

the timeout to a longer value using the Set Timeout

AT command.

DATA ERROR

There was an incomplete message received, and it

was not enough to form a meaningful response. This

may have been caused by the key being turned off,

or a loose connection, for example. Any monitoring

that was in progress will have been aborted.

?

This is the standard response for a misunderstood

command received on the RS232 bus. Usually it is

due to a typing mistake.

ELM320DSC

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