Service Interaction Protocol
Clear Diagnostic Information
Permanent DTCs: This service does not clear OBD-II permanent DTCs. Those require 3 consecutive successful drive cycles after the fault is repaired.
DTC Lifecycle & Clear Verification Pipeline (0x19 ➔ 0x14 ➔ 0x19)
Automated Fault Auditing, Persistent Erase & Re-Read Verification
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 Structure
Clear Diagnostic Information requests are 4-byte frames containing the SID and a 3-byte GroupOfDTC mask. Try toggling between request (TX), response (RX), and split views, filter by semantic type, inspect byte field definitions, explore alternative values, and export code snippets:
◆ PROTOCOL ANATOMY
0x14 CLEAR DIAGNOSTIC INFORMATION
0x14 RESPONSE
Workflow & Response Pending
Clearing memory (writing to EEPROM or Flash) can be slow. If the operation exceeds ~50ms, the ECU sends NRC 0x78 (Response Pending) to prevent tester timeout. Multiple 0x78 responses may be sent before the final 0x54.
ECU is ready. DTC memory is intact. Diagnostic session active (Default or Extended). Awaiting service request.
Request Processing Flow
Every clear request is validated through a structured 7-gate pipeline before the memory erase operation begins. Each gate has a specific NRC for failure.
54 — single byte, no sub-function echo. DTC memory cleared. Timer reset.Click any step to expand validation logic.
State Machine & Security
The ECU transitions through a defined sequence of states during a clear operation. Security state affects whether the operation proceeds or returns NRC 0x33.
ECU is ready. DTC memory is intact. Diagnostic session active (Default or Extended). Awaiting service request.
Session & Security Matrix
SID 0x14 DTC Clearing Matrix
ClearDiagnosticInformation permissions by GroupOfDTC across diagnostic sessions. Select a row for details.
| GroupOfDTC Mask & Domain | DEFAULT 0x01 | EXTENDED 0x03 | PROGRAMMING 0x02 | Security |
|---|---|---|---|---|
| ✓ | ✓ | ✗ | — | |
| ✓ | ✓ | ✗ | — | |
| ~ | ✓ | ✗ | Steering / ABS | |
| ✓ | ✓ | ✗ | — | |
| ~ | ✓ | ✗ | — | |
| ✓ | ✓ | ✗ | — |
Security State Behavior
Standard emission groups (0xFFFF33) and common powertrain DTCs can be cleared in extended sessions without security unlocking. Safety-critical ECUs (airbag, powertrain controller) require security access before allowing all DTCs (0xFFFFFF) to be cleared.
Full erasure of fault memory, freeze frames, and internal failure counters is permitted.
Triggered when this service or requested resource requires an active security unlock that has not been granted.
Triggered during unlock attempts if the calculated key fails ECU cryptographic verification.
Enforced delay lockout if the maximum number of failed key submissions (typically 3) has been exceeded.
Service Dependencies
0x14 erases non-volatile fault logs and resets DTC status masks. Select a node to inspect protocol interactions.
What Gets Cleared & Preserved
SID 0x14 clears specific memory regions within the targeted GroupOfDTC range. Configuration, security, and adaptive data are always preserved.
Click any item to see detailed explanation.
Memory Management
Understanding EEPROM/Flash layout helps diagnose clearing failures and explains why some data survives a clear operation while other data does not.
Click any segment in the bar to inspect the memory region.
Click any step to see its detailed description.
Common Testing Scenarios
Five real-world test cases. Select a scenario, then press Play or step frame-by-frame with ›. Hover any frame to copy its hex bytes.
Extended session · vehicle stationary · no active faults
3 DTCs erased, memory verified empty
Service Interaction Workflows
Animated workflow runner showing how SID 0x14 integrates with other services. Select a scenario and press Simulate to see the full byte-level interaction.
Complete technician sequence: diagnose → physical repair → clear → verify clean.
Full Workflow · 10 frames10 03Enter Extended Session50 03Session Confirmed19 02 AFRead All Active DTCs59 02 AF …DTCs Returned14 FF FF FFClear All DTCs7F 14 78Response Pending54Clear Complete19 02 AFVerify Empty59 02 AF 00No DTCsPress Simulate to animate the full message sequence.
Negative Response Codes
EXCEPTION_MATRIX_V3
The clear request byte count is invalid. SID 0x14 requires 4 bytes: SID + 3-byte groupOfDTC.
This negative response indicates a rejection while processing the Clear Diagnostic Information (SID 0x14) request. Verify preconditions, session levels, and message formatting per ISO 14229.
Troubleshooting & Debugging
Interactive diagnostic checklist and issue cards for common clear failures. Work through the checklist systematically before escalating.
DTCs ReturnCRITICALDTCs reappear immediately after successful 0x54
0x22HIGHNRC 0x22 — Conditions Not Correct
0x33HIGHNRC 0x33 — Security Access Denied
0x13MEDNRC 0x13 — Incorrect Message Length
0x31LOWNRC 0x31 — Request Out of Range
0x72HIGHNRC 0x72 — General Programming Failure
Best Practices & Quick Reference
Immediate 0x54
May send 1× NRC 0x78
1–3× NRC 0x78
3–10+ NRC 0x78
NRC 0x78 is not an error. It signals “processing — keep waiting.” Reset P2* timer (5000ms) on every 0x78 received and continue until 0x54 or a real error NRC arrives.
0x130x220x310x330x720x780x54