Unified Diagnostic Services (UDS) Explained - A Simple Intro [2022]

Summary

This video explains Unified Diagnostic Services (UDS) and its applications in automotive diagnostics. It covers UDS functionality over the CAN bus, including services like reading diagnostic trouble codes (DTCs) and vehicle parameters, and highlights use cases such as telematics for OEM prototype vehicles and predictive maintenance for heavy-duty fleets. The video also introduces the transport protocol ISO-TP and demonstrates how UDS can be used to collect real-time data for analysis, making it an essential tool for modern vehicle diagnostics and maintenance.

Takeaways

• 😀 UDS (Unified Diagnostic Services) is a diagnostic communication protocol used across different vehicle ECUs for tasks such as troubleshooting, firmware updates, and testing.
• 😀 UDS follows a client-server model, where the client (diagnostic tool) communicates with the server (vehicle ECU) for requesting diagnostic information.
• 😀 The UDS protocol supports multiple communication channels, including CAN bus, KWP 2000, LIN, and Ethernet, with CAN being one of the most common.
• 😀 The UDS protocol uses **ISO-TP** (ISO 15765-2) for multi-frame message transmission, enabling larger payloads than the 8-byte limit of Classic CAN.
• 😀 A UDS message typically includes a Protocol Control Information (PCI), Service Identifier (SID), Sub-function byte, and Data Identifier (DID).
• 😀 UDS can be used to extract vital vehicle data such as Diagnostic Trouble Codes (DTCs), VIN (Vehicle Identification Number), and sensor parameters like state of charge in electric vehicles.
• 😀 The process of using UDS to request vehicle data includes generating diagnostic requests and handling multiple frames to gather larger amounts of data.
• 😀 Real-world applications of UDS include vehicle diagnostics (e.g., retrieving DTCs), monitoring sensor data (e.g., battery charge), and predictive maintenance for fleets.
• 😀 UDS allows vehicle data to be extracted and processed using various tools, such as **CANedge2** for data logging and **Vector tools**, **Python**, or **MATLAB** for analysis.
• 😀 Predictive maintenance models rely on large amounts of training data, which can be collected via UDS, including sensor data and classification results (e.g., fault/no fault).

Q & A

What is Unified Diagnostic Services (UDS)?

UDS (Unified Diagnostic Services) is a communication protocol used in the automotive industry for diagnostics, firmware updates, and ECU testing. It enables a client (typically a diagnostic tool) to communicate with a vehicle's Electronic Control Units (ECUs) to request data, troubleshoot, and perform diagnostic tasks.

How does UDS communication work in the context of CAN bus?

UDS communication works by using a client-server model. The client (diagnostic tool) sends requests to the vehicle's ECU over the CAN bus. The ECU, acting as the server, responds with the requested data. UDS over CAN uses multiple frames to transmit large amounts of data, facilitated by the ISO-TP (ISO 15765-2) transport protocol.

What is the role of ISO-TP in UDS over CAN?

ISO-TP (ISO 15765-2) is a transport layer protocol that allows UDS messages to be sent over CAN by splitting large data payloads into multiple frames. These frames are then reassembled to retrieve the complete message. It is essential for handling data that exceeds the size limit of a single CAN frame.

What are the typical services provided by UDS?

UDS provides a wide range of services, such as reading and writing data to ECUs, accessing diagnostic trouble codes (DTCs), and performing firmware updates. Specific services include 'Read Data by Identifier' (0x22), 'Read DTC' (0x19), and 'Diagnostic Session Control' (0x10), among others.

How does UDS differ from OBD2 in terms of functionality?

While both UDS and OBD2 serve diagnostic functions in vehicles, UDS is more advanced and versatile. OBD2 is primarily focused on emissions-related diagnostics and limited to basic vehicle parameters, while UDS provides more detailed access to ECU data and supports a broader range of services, including firmware updates and in-depth vehicle diagnostics.

Can you provide an example of using UDS to request data from a vehicle?

An example is requesting the State of Charge (SoC) from an electric vehicle (EV) like the Nissan Leaf. The diagnostic tool sends a UDS request using the 'Read Data by Identifier' service (0x22) and the Data Identifier (DID) for SoC. The ECU responds with the data, which may be spread across multiple CAN frames and reassembled using ISO-TP.

What is the purpose of using diagnostic trouble codes (DTCs) in predictive maintenance?

DTCs are used to identify faults in a vehicle’s systems. In predictive maintenance, DTCs, along with sensor data (e.g., speed, RPM, throttle position), are collected to train predictive models. These models can then forecast potential failures, allowing for proactive repairs and reducing downtime in fleets of vehicles.

What are some use cases for UDS in vehicle telematics?

One key use case for UDS in vehicle telematics is in OEM prototype vehicles, where data such as State of Charge (SoC), vehicle speed, and other sensor parameters are collected while the vehicle operates in the field. This data is transmitted via devices like the CANedge2 and analyzed in the cloud for performance monitoring and diagnostics.

What devices are commonly used for collecting UDS data in vehicles?

Devices such as the CANedge1 and CANedge2 are commonly used to collect UDS data. The CANedge1 stores data offline on SD cards, while the CANedge2 can automatically offload data to cloud servers, making it suitable for real-time monitoring and telematics applications.

What is the significance of VIN (Vehicle Identification Number) in UDS diagnostics?

The VIN (Vehicle Identification Number) is a unique identifier for each vehicle. In UDS diagnostics, extracting the VIN is essential for identifying the vehicle and linking diagnostic data to a specific unit. It is often retrieved through a UDS 'Read Data by Identifier' request (0x22), where the VIN is stored as a data identifier.