# TelAF diagnostic

Source: [https://docs.qualcomm.com/doc/80-41102-1/topic/telaf_diagnostic.html](https://docs.qualcomm.com/doc/80-41102-1/topic/telaf_diagnostic.html)

TelAF diagnostic services use a set of standardized functions and protocols that allow
            communication between electronic control units (ECUs) within a vehicle and external
            diagnostic tools. These services enable technicians and engineers to monitor, diagnose,
            configure, and troubleshoot the vehicle's electronic systems, components, and
            sensors.

The diagnostic service uses the information exchange initiated by a client to require
            diagnostic information from a server or/and to change its behavior for diagnostic
            purpose.

The following are some primary types of services provided by diagnostic services.

- **Diagnostic Session Control**: Diagnostic sessions define the context and scope
                of diagnostic communication. Services related to diagnostic session control allow
                the diagnostic tool to start, end, and switch between different diagnostic sessions
                based on the tasks being performed.
- **Read Diagnostic Trouble Codes (DTCs)**: This service allows diagnostic tools to
                retrieve stored diagnostic trouble codes (DTCs) from ECUs. DTCs provide information
                about faults or malfunctions in different vehicle systems.
- **Clear Diagnostic Trouble Codes**: Technicians can use this service to clear or
                reset stored DTCs in ECUs after repairs have been performed and issues
                resolved.
- **Communication Control**: These services manage the communication parameters and
                protocols between the diagnostic tool and the ECUs. They ensure that data exchange
                occurs smoothly and efficiently.
- **Security Access Control**: Some diagnostic services require security access to
                perform certain actions, such as ECU programming or advanced configuration. These
                services handle security mechanisms and authorization levels.
- **Upload/Download Data**: Diagnostic services support the transfer of data
                between the diagnostic tool and the ECUs. This can include uploading data from ECUs
                (for example event logs) or downloading data to ECUs (for example calibration
                files).

- **[Architecture overview](https://docs.qualcomm.com/doc/80-41102-1/topic/architecture_overview.html)**
- **[Security system configuration](https://docs.qualcomm.com/doc/80-41102-1/topic/security-system-configuration.html)**
- **[Configurations](https://docs.qualcomm.com/doc/80-41102-1/topic/configurations-diag.html)**
- **[Set up diagnostic testing environment](https://docs.qualcomm.com/doc/80-41102-1/topic/set_up_diagnostic_testing_environment.html)**

Last Published: Aug 06, 2026

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