Service Interaction Protocol
Clear Diagnostic Information
Permanent DTCs: This service typically does not clear “Permanent DTCs” (as defined by OBD-II). Those usually require a successful driving cycle to clear automatically by the ECU logic.
Overview
“The client uses this service to clear one or more units of diagnostic information from the server’s memory. This includes DTCs, captured data, and status counters.”
Message Format
Request Format
Byte | Field | Value | Description |
|---|---|---|---|
| 0 | SID | 0x14 | Clear Diagnostic Information |
| 1 | GroupOfDTC (High) | 0x00–0xFF | DTC Group Mask (High Byte) |
| 2 | GroupOfDTC (Mid) | 0x00–0xFF | DTC Group Mask (Middle Byte) |
| 3 | GroupOfDTC (Low) | 0x00–0xFF | DTC Group Mask (Low Byte) |
Response Format
Byte | Field | Value | Description |
|---|---|---|---|
| 0 | Response SID | 0x54 | Positive Response (SID + 0x40) |
Group of DTC Parameter
The 3-byte GroupOfDTC parameter allows specific targeting of fault groups. The most common use case is clearing all code.
Clears all diagnostic info including DTCs, freeze frames, and extended data.
Request
14 FF FF FFTargets only OBD-II/Emissions related faults.
Request
14 00 00 00Example: Targeting only P-codes (implementation dependent).
Request
14 FF FF 00Example: Targeting only communication U-codes.
Request
14 C0 00 00Workflow & Response Pending
Internal logic flow for clearing diagnostic information from memory.
Clearing memory (writing to EEPROM or Flash) can be a slow operation. If it takes longer than the standard response time (approx 50ms), the ECU will send NRC 0x78 (Response Pending). This tells the tester to wait and prevents a timeout.
Long Operation Workflow (NRC 0x78)
5 stepsNegative Response Codes
Logic_Exceptions