Service Interaction Protocol
Write Data By ID
STORAGE
VALIDATION
RISK_LEVEL
High Risk: Writing incorrect configuration or calibration data can lead to permanent ECU malfunction (“bricking”).
Overview
“The WriteDataByIdentifier service is used by the client to write a data record value to a server, specified by a data identifier.”
How UDS Write operations move data from the Tester into Permanent ECU Storage.
Default Behavior
By default, most writable DIDs are protected from ad-hoc modification. Information written via service 0x2E is typically stored in Non-Volatile Memory (NVM) and persists across power cycles. Successfully writing to a DID requires the ECU to be in a specific session (usually Extended 0x03) and often requires a Security Access (0x27) unlock.
Interactions & Prerequisites
Required State
Verification
Always follow a Write (0x2E) with a Read (0x22) to verify the data was persisted correctly in Non-Volatile Memory (NVM).
Common Writable DIDs
DID | Name | Expected Length | Security Lvl |
|---|---|---|---|
| 0xF190 | VIN | 17 Bytes | Level 1 |
| 0xF18C | Serial Number | Variable | Level 1 |
| 0xFD00 | Calibration | Variable | Level 2 |
| 0xF187 | Part Number | Read-Only | ✗ Locked |
Protocol Anatomy (Write VIN)
◆ PROTOCOL ANATOMY
0x2E WRITE DATA BY ID
0x2E RESPONSE
TX/RX Examples
Write VIN (Successful Sequence)
Enter Extended
10 03Success
50 03...Unlock Sec
27 01... [etc]Write VIN
2E F1 90 57 42 41...Success
6E F1 90UML Sequence Diagrams
Configuration Write & Verification
4 stepsNegative Response Codes (NRCs)
Error_Catalog