Why is separate K-line interface needed?

[Tom1337]

Hello!

This question is mostly for developers ... why does Multiecuscan need separate K-line interface, since ELM327 supports BOTH K-line protocols (ISO 9141-2, ISO 14230-4)? I really don't understand it. Thanks for the answer!

[yani]

Because it does not support the Fiat protocols...

[Tom1337]

Fiat protocols?

There are no Fiat protocols on signal level ... only on higher (application) levels ... So I don't understand your explanation.

[yani]

On signal level it is all serial data with different baud rates. Although Fiat has its own mind about the timings...
The difference is in the data and data frames which are sent/received between the interface and the car.
The ELM interface does NOT support the Fiat protocols, and Fiat uses many different protocols (especially for the older modules before year 2000). Even the ISO9141 of ELM is not compatible with Fiat's ISO9141 because of a small difference in the init sequence.

[Tom1337]

On signal level it is all serial data with different baud rates. Although Fiat has its own mind about the timings...
The difference is in the data and data frames which are sent/received between the interface and the car.
The ELM interface does NOT support the Fiat protocols, and Fiat uses many different protocols (especially for the older modules before year 2000). Even the ISO9141 of ELM is not compatible with Fiat's ISO9141 because of a small difference in the init sequence.

So the problem is only in that init sequence?

Data and data frames cannot be the problem, since the signal protocol does not describe their meaning. Take CAN - if you have CAN interface, you connect on whichever vehicle that has CAN enabled diagnostics, but apart from OBD2, different brands have different application level protocols. But you can still take any CAN interface and interpret data correctly, being ELM327 or 3000€ diagnostic machine.

That's why I cannot see the difference between VAG-COM K-line and ELM327 K-line ... ?!

[tzok]

ELM327 does not offer a RAW mode, so it supports only the protocols it supports You cannot just send a byte or read a byte with given baudrate using ELM327.