Clear Diagnostic Information (0x14) Service in UDS Protocol

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oopener">UDS Protocol. I’m excited to introduce you to one of the essential services in the UDS protocol: Clear Diagnostic Information (0x14). This service is used to clear Diagnostic Trouble Codes (DTCs) stored in a vehicle’s ECU memory. Clearing DTCs is a key step in resetting fault conditions and preparing a vehicle for re-evaluation. It helps technicians manage fault logs, improve service workflows, and ensure the vehicle is operating properly. In this post, I’ll explain how the 0x14 service works, its message structure, and the safety considerations involved. We’ll also walk through real-world examples to see it in action. By the end, you’ll have a solid grasp of when and how to use this command effectively in diagnostics. Let’s get started!

Introduction to Clear Diagnostic Information (0x14) Service in UDS Protocol

In the world of automotive diagnostics, managing and resetting Diagnostic Trouble Codes (DTCs) is crucial for maintaining vehicle health. The Clear Diagnostic Information (0x14) service in the UDS (Unified Diagnostic Services) protocol plays a key role in this process. It allows technicians or diagnostic tools to erase stored DTCs from a vehicle’s ECU memory, typically after a repair has been completed or during routine maintenance. This service ensures that only active and current faults remain in the system, improving diagnostic accuracy and reducing confusion caused by outdated error logs. Whether you’re working on a passenger car or a commercial vehicle, understanding how 0x14 works is essential for efficient and compliant diagnostics.

What is Clear Diagnostic Information (0x14) Service in UDS Protocol?

The Clear Diagnostic Information (Service ID: 0x14) is a service defined in the Unified Diagnostic Services (UDS) protocol (ISO 14229), used in automotive systems to clear stored Diagnostic Trouble Codes (DTCs) from an ECU’s non-volatile memory. DTCs are recorded when an ECU detects a fault during vehicle operation. Once the fault has been repaired, this service helps to reset the system, ensuring the memory is clean and the issue is resolved.

Note:

There are no sub-function parameters used by this service.

Purpose of the 0x14 Service in UDS Protocol

1. To erase error records (DTCs) after resolving vehicle faults: Once a vehicle fault has been diagnosed and repaired, the corresponding DTCs remain stored in the ECU’s memory. The 0x14 service allows technicians to clear these error codes, confirming that the issue has been addressed and the system is functioning normally.
2. To prevent confusion caused by outdated or non-active DTCs: Sometimes DTCs may be stored due to temporary or intermittent conditions that are no longer present. If not cleared, these old codes can mislead technicians or cause unnecessary repairs. This service ensures that only relevant, current faults are displayed.
3. To enable accurate re-diagnosis and verification after repairs: Clearing existing DTCs before a test drive allows the ECU to detect and log only new faults if they reoccur. This helps in confirming whether the original issue was truly fixed or if further troubleshooting is needed.
4. To ensure compliance with OEM diagnostic processes: OEMs often specify that DTCs must be cleared after certain actions like firmware flashing, part replacement, or system initialization. Using 0x14 ensures the vehicle follows the manufacturer’s diagnostic and service workflow.
5. Used in maintenance workshops, production lines, or after testing: Whether in a dealership, service garage, or manufacturing facility, technicians use this service to clear memory after tests, repairs, or end-of-line validations. It helps maintain clean records and avoids false fault reports during delivery.
6. To prepare the vehicle for official inspection or emission tests: In some regions, emission tests or vehicle inspections require a clean DTC slate. Clearing DTCs beforehand ensures that past issues don’t affect test results and helps vehicles pass mandatory checks.
7. To avoid unwanted warning lights on the dashboard: Some DTCs trigger MIL (Malfunction Indicator Lamp) or other warning indicators. After the fault is fixed, clearing DTCs ensures these lights are turned off, restoring driver confidence.
8. To improve customer satisfaction and post-service experience: Delivering a vehicle with warning lights off and no error codes helps build customer trust. It confirms that the technician addressed all issues and checked the vehicle’s systems thoroughly.
9. To support ECU reset and stabilization after programming: After ECU reprogramming or configuration, previously stored errors may no longer be valid. Using 0x14 helps stabilize the ECU environment by clearing irrelevant DTCs from past configurations.
10. To maintain proper storage usage in memory-constrained ECUs: ECUs have limited space for storing DTCs. If the memory is full, new faults might not be recorded. Clearing old or resolved DTCs frees up space, ensuring critical new errors are captured.

Why do we need Clear Diagnostic Information (0x14) Service in UDS Protocol?

The 0x14 service plays a crucial role in maintaining the reliability and accuracy of automotive diagnostic systems. Here’s why it’s needed:

1. To Reset ECU Fault Status After Repairs

Once a fault is repaired, the corresponding Diagnostic Trouble Code (DTC) still remains stored in the ECU’s memory. This stored fault information can mislead technicians into thinking the problem still exists. Using the Clear Diagnostic Information (0x14) service helps reset the fault status, confirming the issue has been addressed. This ensures the ECU reflects the current condition of the vehicle. It also prevents unnecessary re-checks or repeated diagnostics for the same issue.

2. To Avoid Misleading Future Diagnostics

Old or inactive DTCs can remain in the memory even after a fault no longer exists. If these are not cleared, they may confuse technicians during future diagnostic sessions. Using 0x14 removes these irrelevant records and ensures that the next diagnosis is based only on active, real-time faults. This helps in making accurate decisions during vehicle maintenance. It also saves time and prevents incorrect part replacements.

3. To Turn Off Warning Lights

Certain faults stored as DTCs trigger the illumination of warning lights on the dashboard, like the MIL (Malfunction Indicator Lamp). Even if the issue has been fixed, the light may stay on until the DTC is manually cleared using 0x14. This service is essential for turning off such lights and restoring a normal dashboard appearance. It also assures the vehicle owner that the issue has been resolved. A functioning dashboard display is crucial for driver confidence.

4. To Free Up Memory Space in ECUs

ECUs have limited storage space to record DTCs. If not cleared, these codes can occupy memory, leaving no room for new fault entries. The 0x14 service clears old or unnecessary DTCs, ensuring that memory is available for future diagnostic records. This maintains the ECU’s efficiency and prevents memory overflow errors. In systems with continuous monitoring, freeing up space is critical for ongoing diagnostics.

5. To Validate Repair Effectiveness

After using the 0x14 service to clear DTCs, technicians often perform a test drive. If the same DTC reappears, it indicates that the fault is still present or the repair was ineffective. If it doesn’t, the repair is confirmed successful. This process helps validate the quality of maintenance work. It also prevents the delivery of a vehicle that might still have unresolved issues.

6. To Meet OEM Compliance Requirements

Automotive OEMs often have strict standards for diagnostics and repair. Clearing DTCs is a required step after firmware updates, component replacements, or factory testing. The 0x14 service helps fulfill this compliance in a standardized way. It ensures that vehicles meet quality and regulatory requirements before leaving the factory or workshop. This is especially important during end-of-line testing or warranty claims.

7. To Prepare the Vehicle for Emissions or Regulatory Inspections

Vehicles with active DTCs may fail emissions tests or other regulatory inspections. Before these tests, workshops use the 0x14 service to clear inactive or historical codes. This ensures that only current issues affect the test results. It increases the chances of the vehicle passing the inspection. In regions with strict vehicle health checks, this step is critical.

Syntax of 0x14 SID Request Message Frame Format

Data Byte	Parameter Name	Byte Value
#1	Clear Diagnostic Information Request SID	0x14
#2 #3 #4	Group Of DTC[] = [                                  group Of DTC High Byte                    group Of DTC Middle Byte                    group Of DTC Low Byte ]	0x00 – 0xFF 0x00 – 0xFF 0x00 – 0xFF

Syntax of 0x14 SID Positive Response Message Frame Format

Data Byte	Parameter Name	Byte Value
#1	Clear Diagnostic Information +Ve Positive Response SID	0x54

Syntax of 0x14 SID Negative Response Message Frame Format

Data Byte	Parameter Name	Byte Value
#1	Clear Diagnostic Information –Ve Positive Response SID	0x7F
#2	Requested SID [ byte#1 ]	0x14
#3	Negative Response Code [ byte#1 ]	NRC

Supported Negative Response Codes (NRCs) for SID (0x14)

NRC	Parameter Name	Description
0x13	Incorrect Message Length Or Invalid Format	This Negative Response Code (NRC) shall be sent if the length of the message is incorrect.
0x22	Conditions Not Correct	This Negative Response Code (NRC) shall be sent if the operating conditions of the server do not meet the requirements to perform the required action.
0x31	Request Out Of Range	This NRC shall be returned if the specified group Of DTC parameter is not supported.
0x72	General Programming Failure	This Negative Response Code (NRC) shall be returned if the server detects an error when writing to a memory location.

Example of Clear Diagnostic Information (0x14) Service in UDS Protocol

In UDS (Unified Diagnostic Services), the 0x14 service is used to clear one or more Diagnostic Trouble Codes (DTCs) stored in an ECU. This is essential after faults have been repaired so that the system can re-monitor and log new, relevant data.

Clear Diagnostic Information Request Message Flow Example

Message direction	Client → Server
Message Type	Request
Data Byte	Description (all values are in hexadecimal)	Byte Value
#1	Clear Diagnostic Information Request SID	0x14
#2 #3 #4	Group Of DTC [ DTC High Byte ] (“Emissions-related systems”) Group Of DTC [ DTC Middle Byte ] Group Of DTC [ DTC Low Byte ]	0xFF 0xFF 0x33

Clear Diagnostic Information Positive Response Message Flow Example

Message direction	Server → Client
Message Type	Response
Data Byte	Description (all values are in hexadecimal)	Byte Value
#1	Clear Diagnostic Information +Ve Response SID	0x54

Clear Diagnostic Information Negative Response Message Flow Example

Message direction	Server → Client
Message Type	Response
Data Byte	Description (all values are in hexadecimal)	Byte Value
#1	Clear Diagnostic Information –Ve Response SID [ byte#1 ]	0x7F
#2	Requested SID [ byte#1 ]	0x14
#3	Negative Response Code [ byte#1 ]	NRC

Example of Clear Diagnostic Information (0x14) SID Request and Positive Response Frame Format

Request Frame Format:

PCI Length	Request SID	DTC
0x04	0x14	0xFF	0xFF	0x33

Positive Response Frame Format:

PCI Length	Response SID	DTC
0x04	0x54	0xFF	0xFF	0x33

Example of Clear Diagnostic Information (0x14) SID Request and Negative Response Frame Format

Request Frame Format:

PCI Length	Request SID	DTC
0x05	0x14	0xFF	0xFF	0x33

Negative Response Frame Format:

PCI Length	Response SID	SID	NRC
0x03	0x7F	0x14	13

Advantages of Clear Diagnostic Information (0x14) in UDS Protocol

Here are the advantages of using the Clear Diagnostic Information (0x14) service in the UDS protocol:

1. Facilitates Accurate Re-diagnosis: By clearing obsolete or irrelevant Diagnostic Trouble Codes (DTCs), the system can perform a fresh diagnostic check, ensuring that newly identified faults are accurately logged after repairs and preventing old errors from interfering with new diagnostics.
2. Supports Compliance with OEM Standards: The 0x14 service allows automotive service providers to follow OEM diagnostic protocols, ensuring compliance with factory standards and avoiding errors in diagnostic reporting.
3. Improves System Performance and Accuracy: Clearing out stale or inactive DTCs helps the ECU perform better by ensuring the system operates with only current, relevant data, resulting in faster, more accurate diagnostics and preventing the misidentification of old issues.
4. Essential for Post-Repair Testing: After major repairs, such as ECU programming, sensor replacements, or software updates, the 0x14 service is necessary to reset the diagnostic memory, ensuring that the vehicle passes all post-repair checks and accurately re-assesses its health.
5. Enhances Maintenance and Serviceability: This service is integral to vehicle maintenance procedures, allowing technicians to clear codes once issues are resolved, ensuring that only accurate, relevant service records are kept, and improving the vehicle’s overall operational state.
6. Reduces Customer Complaints and Misdiagnosis: By clearing old fault codes after repairs, the 0x14 service prevents confusion and misdiagnosis, helping to improve customer satisfaction by ensuring that the diagnostic results reflect the vehicle’s current condition.
7. Optimizes Fault Tracking and Monitoring: The ability to clear specific DTC groups allows technicians to efficiently manage multiple fault categories, improving troubleshooting by focusing on the most relevant issues while avoiding unnecessary alerts from unrelated systems.
8. Ensures Clear Error History for Future Service: Clearing resolved DTCs ensures that only active or unresolved issues remain in the system, which helps future technicians accurately track current problems, making future repairs or services more efficient.
9. Compliance with Vehicle Health Monitoring Systems: Clearing DTCs after resolving an issue helps maintain compliance with onboard vehicle health monitoring systems, ensuring that the vehicle is accurately represented in tracking systems, affecting resale value and safety status.
10. Improves Communication Between Diagnostic Tools and ECUs: The 0x14 service ensures smooth communication between diagnostic tools and ECUs by clearing old fault codes, preventing errors in the data exchange process and providing a clean diagnostic slate for efficient repairs and diagnostics.

Disadvantages of Clear Diagnostic Information (0x14) in UDS Protocol

Here are the disadvantages of using the Clear Diagnostic Information (0x14) service in the UDS protocol:

1. Risk of Losing Critical Diagnostic Information: When DTCs are cleared, important error history might be lost. This can be a disadvantage if a fault recurs later and there’s no record of previous issues to help with diagnosing the root cause, making future troubleshooting more difficult.
2. Potential for Misleading Diagnostics: Clearing DTCs prematurely can lead to a situation where a vehicle is thought to be free of faults even if the underlying issue hasn’t been fully resolved. This could result in a false sense of security and potentially overlook persistent issues.
3. Limited Use in Certain Fault Conditions: The 0x14 service is typically useful only when the faults are fully resolved. If there are issues with clearing the DTCs (for example, if a fault persists despite clearing), the ECU may not be able to effectively communicate the status of the repair, hindering effective diagnostics.
4. Overuse Can Lead to Unnecessary Diagnostic Reset: Overuse of the 0x14 service can lead to frequent clearing of DTCs even when it’s unnecessary. This can disrupt the natural diagnostic flow and create confusion during troubleshooting, especially when it’s not clear whether a fault has actually been fixed.
5. Can Hide Recurrent Issues: If the 0x14 service is used without proper investigation, it may clear diagnostic codes that point to recurrent problems. As a result, new repairs might be made without fully addressing the root cause, leading to repeated failures and unnecessary repairs.
6. Compatibility Issues with Certain ECUs: Not all ECUs are designed to handle 0x14 service correctly, and in some cases, certain vehicle models or ECU types may not fully support the clearing of diagnostic information. This can lead to compatibility issues, where the 0x14 service might not be executed properly.
7. Increased Time for Reprogramming or Re-initialization: In some cases, clearing diagnostic information may require additional steps to reinitialize or reprogram the ECU. This can lead to delays during repairs, as the ECU may need to go through a series of steps to reconfigure itself after clearing the DTCs.
8. May Not Solve the Underlying Problem: Clearing DTCs does not necessarily fix the root cause of the problem. If the issue is not properly addressed, the fault can recur, and the diagnostic process will need to be repeated, leading to potentially longer repair times.
9. Possibility of Errors in Fault Categorization: If the 0x14 service is not used carefully, it might clear diagnostic information related to non-critical faults that are still important for future diagnostics. This could lead to inaccurate fault categorization, affecting the accuracy of the repair process.
10. Risk of Incomplete Data for Legal or Warranty Purposes: In some regions, clearing DTCs might interfere with legal or warranty requirements. Some diagnostic information may need to be retained for compliance purposes, and clearing it could result in violations of legal or contractual obligations, especially in the case of vehicles under warranty.

Future Development and Enhancement of Clear Diagnostic Information (0x14) in UDS Protocol

The future development and enhancement of the Clear Diagnostic Information (0x14) service in the UDS protocol will likely focus on improving flexibility, security, and integration with modern diagnostic systems. Here are some possible areas of improvement:

1. Enhanced Security Features: As automotive systems become increasingly connected, security will become a key focus. Future versions of 0x14 may include more robust security measures, such as encryption and authentication, to prevent unauthorized users from clearing diagnostic information and tampering with the vehicle’s fault history. These enhancements will ensure that only authorized personnel can use the 0x14 service to clear DTCs.
2. Integration with Cloud-Based Diagnostics: With the rise of connected vehicles, cloud-based diagnostic services are becoming more common. The 0x14 service may evolve to work seamlessly with cloud platforms, allowing for real-time data updates and sharing of diagnostic information across networks. This could improve remote diagnostics and allow service centers to access a more comprehensive history of the vehicle’s faults and repairs.
3. Improved Compatibility Across ECUs: Currently, there can be compatibility issues with certain ECUs, and different manufacturers might implement the 0x14 service in slightly different ways. In the future, standardization efforts may result in 0x14 being universally supported across all vehicle ECUs, ensuring consistent behavior and performance across different platforms and manufacturers.
4. Intelligent Fault Management: Future versions of the 0x14 service might feature more intelligent fault management, allowing the system to only clear non-critical or resolved DTCs automatically while keeping a record of recurring issues. This could help ensure that the most relevant diagnostic information is preserved, reducing the risk of prematurely clearing important data.
5. Integration with Predictive Maintenance: As predictive maintenance technologies improve, 0x14 could be enhanced to work with predictive diagnostics systems. This would allow for more accurate and timely clearing of DTCs based on real-time vehicle performance data and historical trends, helping identify when certain faults are likely to occur again.
6. Enhanced User Interface for Service Technicians: In future developments, service technicians may benefit from more intuitive interfaces when clearing DTCs. Visual aids, more detailed error descriptions, and context-aware prompts could make the 0x14 service easier to use, reducing human error and increasing the efficiency of diagnostics in service centers.
7. Support for More Advanced Fault Clearing Methods: Instead of simply clearing DTCs, future enhancements might allow for more advanced fault clearing methods that involve automatically adjusting ECU configurations, resetting adaptation data, or performing system recalibrations after clearing certain fault codes. This could help ensure that the system operates optimally after repairs or service.
8. Compliance with Emerging Regulations: As vehicle regulations evolve, the 0x14 service may need to be updated to comply with new standards or legal requirements. This could include features like automatic logging of diagnostic information for audit purposes or restrictions on clearing certain types of critical DTCs in specific regions or markets.
9. Better Fault History Tracking: Future improvements could include better tracking of fault history even after the 0x14 service has been used. This might include recording a detailed log of when and why DTCs were cleared, providing more transparency and accountability for the actions taken on the vehicle’s diagnostic system.
10. Integration with Autonomous Vehicle Diagnostics: With the development of autonomous vehicles, diagnostic systems will need to become even more sophisticated. The 0x14 service may be enhanced to handle complex fault-clearing processes that involve multiple ECUs and sub-systems, helping to maintain the integrity of diagnostics in autonomous driving systems.