ISO 91412 Road Vehicles- Diagnostic Systems

Name: Matestlab Inc.
Address: 2093 Philadelphia Pike, Claymont, Delaware, 19703, US
Telephone: (302)244-7710

Introduction to ISO 91412

ISO 91412 is an international standard that specifies the diagnostic communication protocol used for the communication between electronic control units (ECUs) in road vehicles. This standard provides a standardized method of communication between ECUs and diagnostic tools, which is essential for the diagnosis and repair of automotive systems.

This standard specifies the physical layer requirements for communication between the diagnostic equipment and the vehicle’s ECUs. This standard provides the requirements for the K-line, which is a single-wire serial communication protocol that is used for diagnostic purposes in road vehicles.

ISO 91412 Test Method

The procedure for using ISO 9141-2 involves connecting a diagnostic tool to the vehicle’s diagnostic connector, which is typically located under the dashboard. The diagnostic tool then sends commands to the vehicle’s ECUs using the K-line protocol specified in ISO 9141-2. The ECUs respond with diagnostic data, which is then displayed on the diagnostic tool for analysis. The following table outlines the testing procedure:

Steps	Description
1	The diagnostic tool is connected to the ECU using a cable that meets the requirements of the ISO 9141-2 standard.
2	Power on the ECU and initiate communication with the diagnostic tool.
3	A start communication message is sent to the ECU.
4	The response indicates that the ECU has entered diagnostic mode.
5	A request for identification message is sent to the ECU.
6	The response contains identification information for the ECU.
7	A request for diagnostic trouble codes (DTCs) message is sent to the ECU.
8	The response contains a list of any DTCs stored in the ECU.
9	A request for data message is sent to the ECU.
10	The response contains data values for the requested parameters.
11	A stop communication message is sent to the ECU.
12	The response indicates that the ECU has exited diagnostic mode.
13	Next, one has to power off the ECU and disconnect the diagnostic tool.

ISO 91412 Specimens

ISO 9141-2 does not involve any physical specimens as it is a standard for communication protocols used in vehicle diagnostics.

ISO 91412 Results

ISO 9141-2 is an essential standard in the automotive industry as it provides a standardized method of communication between ECUs and diagnostic equipment. The K-line protocol specified in this standard is used for diagnostic purposes in road vehicles and is crucial for identifying and repairing problems with the vehicle’s systems.

ISO 9141-2 is a diagnostic communication protocol and is similar to other standards of the same nature. ISO 14230-4 (also known as Keyword Protocol 2000 or KWP2000) is a related standard that specifies a similar communication protocol for diagnostic communication between road vehicles and diagnostic equipment. KWP2000 is a more modern and advanced protocol than ISO 9141-2 and is used in newer vehicles.

Updated on September 17, 2026

About Author

Divakar Shukla

Divakar Shukla is an Electrical and Electronics Engineer specializing in the convergence of embedded systems architecture, industrial automation, and applied artificial intelligence.
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ISO 91412 Road Vehicles- Diagnostic Systems

Introduction to ISO 91412

ISO 91412 Test Method

ISO 91412 Specimens

ISO 91412 Results

Tests related to ISO 91412

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