Does someone know for sure what protocol Honda uses on their K-line?
Is this ISO9141-2?
I found some
specific information on protocol but it is hard to understand for me. May be someone could explain me this in simple words?
Communication Line and Interface
Communication Lines
Most Honda non-OBD (92M to 00M) vehicles are equipped with 3 pin or 5 pin DLC. The "DIAG-H", bi-directional serial communication line, is connected to the DLC and provides serial data stream to the PGM TESTER in 92Hm/2 protocol.
The other side, Honda OBD compliance vehicles are equipped with 16 pin DLC conformed to SAE J1962 / ISO 15031-3 for the off-board diagnostic communication. Mainly, 92Hm/2 protocol is used for the Chassis/Body System
ECUs.
There then was the 95Hm-CARB Protocol which supported some OBD2 protocol structures. This protocol has a higher baud rate of about 10.4 kbps
+ 5bps (For ISO 9141-2 Initialization Address Signal)
95Hm-CARB Protocol
The CARB OBD2 regulation prescribes SAE J1979 for the diagnostic communication between the vehicles and the OBD2 Scan Tool. It is necessary to implement SAE J1979 to conform with the regulation. However, this prescribed communication protocol can not cover HONDA specified diagnostic methods of the PGM TESTER/HDS for the PGM-FI.
The 95Hm-CARB protocol is defined for the PGM-FI system on the Honda OBD2 vehicles to conform with the CARB OBD2 regulation and to succeed of the existing diagnostic functions of the PGM TESTER/HDS.
The PGM-FI ECU equips the communication I/F of ISO9141-2 K-LINE to comply with CARB OBD2 / EPA OBD regulations. The K-LINE, bi-directional serial communication line, is connected to the terminal 7 of the SAE J1962 DLC. ISO9141-2 L-LINE is not used for the communication.
ISO9141-2 is selected as diagnostic communication protocol for the 95M- Honda PGM-FI ECU to conform with the CARB / EPA regulation. And 95Hm-CARB protocol is used on the K-LINE of ISO9141-2 serial interface. This protocol supports both SAE J1978 OBD Scan Tool and Honda PGM TESTER.
The Network Address of this protocol supports:
mode‘C’ ; For SAE J1978 Scan Tool Master / Slave, Single Request / Multiple Response
mode‘H’ ; For Honda PGM TESTER/HDS Master / Slave, Single Request / Single Response
No other ECU than PGM-FI is allowed on K-LINE.
There then came the H/99 Protocol
H/99 protocol is extended from 95Hm-CARB protocol to support ISO9141-2 communication controls completely. This newly established communication protocol allows other ECU(s) to be connected to the ISO9141-2 K-LINE.
Two communication mode, mode'H' for PGM TESTER and mode'C' for J1978 Scan Tool, are available and each message
sets are compatible with 95Hm-CARB.
In the later years, Honda has implemented CAN.
HDC_CAN (Honda Diagnostic on CAN) protocol. For those of you who dont know what CAN is it is a high speed message protocol used in automotive applications.
