[DannoXYZ]

Underlying hardware and signaling standard is same. For example, using wire that conducts electricity. Digital TTL triggers using 0-12v pulses. Initiate communications with 70ms low, then 120ms high signal. All standardised because OBD2 uses same signals as ISO-9141-2. Since OBD2 is newer standard, it incorporates backwards hardware compatibility with earlier K-line and includes it in connector.

Problem is app for those devices are not compatible with ECM because they use OBD2 language.
Simple.
Only Honda app will talk to ECM using K-line language.

 

[Tamir]

Yes. Like this:

 

[Tamir]

Late update: The project failed. Our ECM does not know how to communicate with OBD2 devices.
As a consolation prize I turned the DLC to OBD2 adapter to a special HONDA TOOL:
SCS Service connector 070PZ-ZY30100