Service Interaction Protocol
Diagnostic Session Control
Standard Sync: Implements ISO 14229-1:2020 logic, including active S3 server timeout detection and session-specific P2/P2* timings.
Service Purpose
“DiagnosticSessionControl enables various diagnostic sessions in the server (ECU). The server always operates within exactly one session, defaulting to the Default Session (0x01) upon every reset event.”
Message Standards
PACKET_INPUT_STRUCT
Byte | Parameter | Data_Type |
|---|---|---|
| 0 | Service ID | 0x10 |
| 1 | Sub-Function | 0x01–0x04 |
PACKET_OUTPUT_STRUCT
Byte | Parameter | Data_Type |
|---|---|---|
| 0 | Response SID | 0x50 |
| 1 | Session Echo | 0x0X |
SERVER_RESPONSE_PARAMS
Byte | Parameter | HUD_Example | Descriptor |
|---|---|---|---|
| 2-3 | P2 Server Timing | 0x00 0x32 | 50ms Resolution |
| 4-5 | P2* Server Timing | 0x13 0x88 | 5000ms Resolution |
Response Management
RESPONSE_SUPPRESSION_LOGIC
Active Bit 7 (0x80) detection. When present in the sub-function byte, the ECU enters Silent Mode for positive responses, optimizing packet throughput.
Request
10 01Response
50 01Suppression_Active
10 81! Critical: NRC 0x7F bypasses suppression logic and will always broadcast.
Session Selection
- Standard diagnostic operations
- DTC retrieval and clearing
- Basic identification
Protocol_Logic
10 01- Advanced service access
- I/O control operations
- Tester Present required
Protocol_Logic
10 03- Software update procedures
- Memory erase operations
- Bootloader access
Protocol_Logic
10 02- Airbag/ABS diagnostics
- Critical routine execution
- High-priority timing
Protocol_Logic
10 04Timing & S3 Timeout
Timing parameters define the window for server responses (P2) and client keep-alive signals (S3). When entering a non-default session, the S3 Server Timeout becomes active, requiring a Tester Present signal every 5000ms.
Operational Constraints
Transitioning between sessions triggers automatic resets of ECU security states and active diagnostic processes to ensure protocol integrity.
System_Subject | Transition_Logic | Constraint_Level |
|---|---|---|
| Security Access (0x27) | Force_Locked | Protocol Requirement |
| Active Downloads (0x34) | Purge_Buffer | Critical Fault |
| Diagnostic Routines (0x31) | Terminate_All | Safety Buffer |
| Communication (0x28) | Default_Mode | Reset Protocol |
Protocol Interaction
Protocol Transition Sequence
2 steps0x01Power-on default. No security required.
0x02Flash reprogramming; requires SecurityAccess.
0x03Advanced diagnostics. Most common non-default.
0x04ASIL-rated system isolation.
- Default → Programming
10 02 - Default → Extended
10 03 - Default → Safety
10 04 - Extended → Programming
10 02 - Any non-default → Default
10 01 / S3 timeout - Safety → Extended
10 030x22 - Programming → Programming
10 020x22 - Safety → Any other
10 xx0x22
Logic_Core: UDS_STATE_MACHINE_ENG
v4.0_READYNegative Responses
Logic_Exceptions