UDS

Last update: 12. April 2023 (Created: 12. April 2023)

UDS

ISO Standard: ISO 14229

Great Article to learn about UDS: https://www.csselectronics.com/pages/uds-protocol-tutorial-unified-diagnostic-services
https://uds.readthedocs.io/en/latest/index.html

UDS Service Identifiers (SIDs)

💡 TIP: To find the Response SID to a Request SID just add 0x40 to it.

Diagnostic and Communication Management

Request SID	Response SID	Service	Details
`0x10`	`0x50`	Diagnostic Session Control	Control which UDS services are available.
`0x11`	`0x51`	ECU Reset	Reset the ECU ("hard reset", "key off", "soft reset").
`0x27`	`0x67`	Security Access	Enable use of security-critical services via authentication.
`0x28`	`0x68`	Communication Control	Turn sending/receiving of messages on/off in the ECU.
`0x29`	`0x69`	Authentication	Enable more advanced authentication (vs. 0x27) via PKI based exchange.
`0x3E`	`0x7E`	Tester Present	Send a "heartbeat" periodically to remain in the current session.
`0x83`	`0xC3`	Access Timing Parameters	View/modify timing parameters used in client/server communication.
`0x84`	`0xC4`	Secured Data Transmission	Send endcrypted data via ISO 15764 (Extended Data Link Security).
`0x85`	`0xC5`	Control DTC Settings	Enable/disable detection of errors (e.g. used during diagnostics).
`0x86`	`0xC6`	Response On Event	Requests that an ECU processes a service request if an event happens.
`0x87`	`0xC7`	Link Control	Set the baud rate for diagnostic access.

Data Transmission

Request SID	Response SID	Service	Details
`0x22`	`0x62`	Read Data By Identifier	Read data from targeted ECU (e.g. VIN, sensor data etc.).
`0x23`	`0x63`	Read Memory By Address	Read data from physical memory (e.g. to understand software behaviour).
`0x24`	`0x64`	Read Scaling Data By Identifier	Read information about how to scale data identifiers.
`0x2A`	`0x6A`	Read Data By Identifier Periodic	Request ECU to broadcast sensor data at slow/medium/fast/stop rate.
`0x2C`	`0x6C`	Dynamically Define Data Identifier	Define data parameter for use in 0x22 or 0x2A dynamically.
`0x2E`	`0x6E`	Write Data By Identifier	Program specific variables determined by data parameters.
`0x3D`	`0x7D`	Write Memory By Address	Write information to the ECU's memory.

Stored Data Transmission

Request SID	Response SID	Service	Details
`0x14`	`0x54`	Clear Diagnostic Information	Delete stored DTCs.
`0x19`	`0x59`	Read DTC Information	Read stored DTCs and related information.

InputOutput Control

Request SID	Response SID	Service	Details
`0x14`	`0x54`	Input Outpu Control By Identifier	Gain control over ECU analog/digital inputs/outputs.

Routine

Request SID	Response SID	Service	Details
`0x31`	`0x71`	Routine Control	Initiate/stop routines (e.g. self-testing, erasing of flash memory).

Upload Download

Request SID	Response SID	Service	Details
`0x34`	`0x74`	Request Download	Start request to add software/data to ECU (including location/size).
`0x35`	`0x75`	Request Upload	Start request to read software/data from ECU (including location/size).
`0x36`	`0x76`	Transfer Data	Perform actual transfer of data following use of 0x74/0x75.
`0x37`	`0x77`	Request Transfer Exit	Stop the transfer of data.
`0x38`	`0x78`	Request File Transfer	Perform a file download/upload to/from the ECU.

Negative Response

Request SID	Response SID	Service	Details
	`0x7F`	Negative Response	Sent with a Negative Response Code when a request cannot be handled.

UDS Example

In this example we want to read the ECU Identification from the ECU (also called "manufacturer spare part number").

For this we use the UDS service Read Data by Identifier (0x22) with the Data Identifier (DID) of 0xF187.

The ECU CAN ID in this example is 0x200 and the Tester CAN ID is 0x100.

Also no padding is used in this example.

CANID   Data                      Explanation
--------------------------------------------------
0x100   03 22 F1 87               # Request length 3 (0x03), SID 0x22, DID 0xF187.
0x200   10 15 62 F1 87 4D 59 5F   # Positive Response (RSID 0x62 DID 0xF187). Multiframe length 21 bytes (0x15). Start of data (ASCII): MY_
0x100   30 00 00                  # Flow Control Tester
0x200   21 45 43 55 5F 49 44 45   # Consecutive Frame with data (ASCII): ECU_IDE
0x200   22 4E 54 49 46 49 43 41   # Consecutive Frame with data (ASCII): NTIFICA
0x200   23 54 49 4F 4E            # Consecutive Frame with data (ASCII): TION

Here we can see that the ECU returns "MY_ECU_IDENTIFICATION" as its ECU identification.