Service Interaction Protocol
ECU Reset
State Impact: Hard Reset (0x01) and Key Off/On Reset (0x02) always revert the ECU to Default Session (0x01) and lock Security Access. Plan workflow accordingly.
Service Purpose
“The ECU Reset service is used to request the server to perform a reset. The server shall simulate the reset condition requested by the sub-function parameter.”
Message Format
Byte | Field | Value | Description |
|---|---|---|---|
| 0 | SID | 0x11 | ECU Reset service identifier |
| 1 | Sub-Function | 0x01–0x05 | Reset type · Bit 7 = Suppress Response (SPRMIB) |
Byte | Field | Example | Description |
|---|---|---|---|
| 0 | Response SID | 0x51 | Positive Response (SID + 0x40) |
| 1 | Sub-Function Echo | 0x01 | Echoes the executed reset subfunction |
| 2 | Power Down Time | 0x05 | Optional — seconds until reset executes |
Reset Types (Sub-Functions)
0x01FULL_CYCLESimulates a complete power cycle. Initializes both hardware and software layers. All volatile memory is cleared. ECU returns to Default Session.
Request
11 010x02IGNITION_CYCLESimulates an ignition key cycle. Gentler than Hard Reset — activates newly written configuration parameters without full hardware reinit.
Request
11 020x03APP_RESTARTRestarts the application software only. Hardware remains live. Fastest reset type — suitable for app hang recovery and quick test resets.
Request
11 030x04REQUIRES_SECURITYConfigures ECU for rapid power-down mode, bypassing normal shutdown sequences. Used in EOL testing and power management validation.
Request
11 040x05REQUIRES_SECURITYRestores normal shutdown behavior after rapid power-down mode was activated. Always paired with subfunction 0x04.
Request
11 05Request Processing & Validation
The ECU processes reset requests through a sequential 5-step validation pipeline. Each gate failure returns a specific NRC. All five must pass before the positive response is sent and reset executes.
51 0X, drains communication, then executes the requested reset type. Comm stack goes offline during reset.Click any step to expand validation logic.
Service Dependencies & Interactions
ECU Reset sits at the top of a dependency stack. Services below it must be active or available for reset to succeed. Click any node to inspect its role, failure mode, and interaction rules.
Session gates which subfunctions are permitted
0x04/0x05 always require unlock; others OEM-defined
Hard/KeyOff always reverts session to Default 0x01
Every reset type relocks security unconditionally
Reset Type vs. Session Matrix
Session availability determines which reset types are accessible. Select a session below to filter the supported reset types and expand any row for detailed requirements.
Select a session to filter. Click a supported reset type for details.
Suppress Positive Response (SPRMIB)
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
11 01Response
51 01Suppression_Active
11 81! Critical: NRC 0x7F bypasses suppression logic and will always broadcast.
Hard Reset
11 01Hard Reset (Suppressed)
11 81ECU State Machine Phases
From request receipt to ECU back online — eight discrete phases. Select a reset type, press Simulate to animate through all states, or click any state node to inspect it directly.
—ECU is fully operational on the diagnostic bus. Ready to receive service requests. Session and security state as last configured.
Press Simulate to animate through all phases, or click any state to inspect it.
Communication State Transitions During Reset
The communication bus goes through four states during a reset. Select a reset type to compare offline durations — the key variable determining how long the tester must wait.
Tester: Do not send requests during COMM_OFFLINE. The ECU cannot respond. Wait until it comes back online, then verify Default Session before any elevated operations.
Select reset type to compare offline durations. Click phase to expand.
Security Requirements by Reset Type
Security requirements vary by subfunction and OEM implementation. Subfunctions 0x04/0x05 universally require security unlock. Others are implementation-dependent.
Reset Type | Security Required? | Level | Typical Use Cases |
|---|---|---|---|
| 0x01 Hard Reset | Optional* | OEM-defined | Post-programming, configuration commit, diagnostic recovery |
| 0x02 Key Off/On | Optional* | OEM-defined | Parameter activation, learned value reset, power-cycle simulation |
| 0x03 Soft Reset | Optional* | OEM-defined | Application restart, quick recovery, test scenarios |
| 0x04 Enable Rapid PD | Required** | 0x27 Unlock | EOL testing, power management validation |
| 0x05 Disable Rapid PD | Required** | 0x27 Unlock | Restore normal shutdown after EOL test |
* Optional (0x01–0x03): ECU and vehicle-specific. Some ECUs allow reset without security access; others require it. Check your ECU’s diagnostic specification.
** Required (0x04–0x05): Rapid Power Down has safety implications. Security unlock via SID 0x27 is mandatory before requesting these subfunctions.
Complete Workflow Examples
Three canonical workflows covering the most common ECU Reset use cases. Select a workflow and run the animated step sequence to trace the full hex exchange.
Full software reprogramming sequence. Uses Hard Reset to apply new firmware after programming session completes all data transfer blocks.
10 02Enter Programming SessionActivates bootloader, enables flash services
27 01Request SeedSecurity level for programming unlock
27 02 <key>Send Computed KeyUnlock security for erase/write ops
28 03Disable Non-Diagnostic CommsIsolate ECU during flash
34 00 44 <addr> <len>Request DownloadDeclare memory write range
36 01..NN <block>Transfer Data BlocksAll firmware blocks sequentially
37Transfer ExitFinalize and checksum verify
11 01Hard Reset ECUApply new firmware via power cycle
—Wait for ECU OnlineTypically 5–10 seconds offline
10 01Verify Default SessionConfirm ECU back online, security locked
Hard Reset Execution
6 stepsTroubleshooting & Common Issues
Work through the diagnostic checklist when a reset request fails or behaves unexpectedly. The issue cards below map NRC codes to root causes and fixes.
Click any issue card to reveal cause and fix.
Quick Reference & Best Practices
At-a-glance reference for all five reset subfunctions with timing, state impact, and use cases. Use the checklist to verify compliance before and after reset operations.
Volatile cleared · NVM preserved · DTC preserved
Negative Response Codes
Error_Catalog