ELM327P datasheet(26/51 Pages) ELM

26 / 51 page

26 of 51

ELM327

ELM327DSC

Elm Electronics – Circuits for the Hobbyist

www.elmelectronics.com

standard now allows 29 in total.

The ELM327 does not normally show any of these

extra bytes unless you turn that feature on with the

Headers On command (AT H1). Issuing that allows

you to see the header bytes and the checksum byte

(for the J1850, ISO 9141 and ISO 14230 protocols).

For the CAN protocols, you will see the ID bits, and

other items which are normally hidden such as the PCI

byte for ISO 15765, or the data length codes (if they

are enabled with PP 29). Note that the ELM327 is not

able to display the checksum information for CAN

systems, or the IFR bytes for J1850 systems.

It is not necessary to ever have to set these

header byes, or to perform a checksum calculation, as

the ELM327 will always do this for you. The header

bytes are adjustable however, should you wish to

experiment by using advanced techniques such as

physical addressing. The next section provides a

discussion on how to do this…

OBD Message Formats (continued)

ELM327P Datasheet(PDF) 26 Page - ELM Electronics