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ELM322SM Datasheet(PDF) 11 Page - ELM Electronics |
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ELM322SM Datasheet(HTML) 11 Page - ELM Electronics |
11 / 18 page Error Messages 11 of 18 ELM322DSF Elm Electronics – Circuits for the Hobbyist < http://www.elmelectronics.com/ > Resetting Trouble Codes When problems occur, the ELM322 will respond with one of the following short messages. Here is a brief description of each… BUS BUSY The ELM322 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 change as expected. This is most likely because of a circuit problem (a short or open), so check all of your wiring carefully. <DATA ERROR There was a problem with the data checksum (CRC byte), indicating a data error in the line pointed to (the ELM322 still shows you what it received). There could have been a circuit problem, or a noise burst which interfered, so try re-sending the request again. DATA ERROR The ELM322 expects at least four bytes for every message, and less than that were received. This may have been caused by the key being turned off, or a loose connection, for example, or by receiving a single byte header message when a three byte header was expected. Any monitoring that was in progress will have been aborted. Try turning the display of headers on to see what was actually sent. NO DATA There was no response from the vehicle before a timeout occurred. The mode requested may not be supported, so the vehicle ignored you, or the timeout value was set too short, or possibly the ignition key was not turned to the ‘on’ position. Try issuing an 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 with the Set Timeout AT command. ? This is the standard response for a misunderstood command received on the RS232 bus. Usually it is due to a typing mistake. The ELM322 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 ELM322, 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 ELM322 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 they 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! ELM322 |
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