How to Clear Permanent DTC Codes? Diagnosing and Repairing

Permanent DTC codes can be a major headache for car owners, as they can indicate a significant problem with the vehicle and cannot be reset with simple tricks. Your check engine light may not be illuminated on the dash but permanent DTC codes are still stored in the ECU, so you should be concerned.

Clearing the DTCs highlights

• Difficulty level:Low
• Needed scan tools:Professional tool or app
• Additional equipment:No other tools needed
• Timeneeded:10-15 minutes
• Price in a shop:$150 - $250
• DIY repair:Possible

What are Permanent DTC Codes?

Understanding how Permanent DTCs work can help prevent further problems and misdiagnosis.

Diagnostic Trouble Codes (DTCs) are a critical component of modern vehicle technology, providing drivers and mechanics with vital information about the performance of their vehicles. However, not all DTCs are created equal, and it's essential to understand the difference between regular DTCs and Permanent Diagnostic Trouble Codes (PDTCs).

PDTCs are similar to regular DTCs in that they both indicate an issue with the car's engine or components. However, the main difference between the two is that PDTCs cannot be cleared or reset by disconnecting the vehicle's battery or using an On-Board Diagnostic (OBD) scan tool. 

So why are PDTCs so important? The primary reason is to ensure that vehicles are 100% compliant with emissions regulations. With PDTCs, vehicles can't pass an in-use inspection simply by disconnecting the battery or clearing DTCs with a scan tool before the inspection. This means that vehicle owners must address any problems indicated by PDTCs, making their vehicles safer and more environmentally friendly.

In addition to emissions compliance, PDTCs are also important for vehicle owners as they can indicate a more serious issue with the vehicle that could impact its performance and safety. 

For example, a PDTC could indicate a problem with the vehicle's catalytic converter, which is essential for reducing emissions and keeping the engine running smoothly. If left unaddressed, a problem with the catalytic converter can lead to more serious engine issues and even damage to other components.

How to Diagnose Permanent DTC Codes

A PDTC is stored when a regular DTC is confirmed, and the Malfunction Indicator Lamp (MIL) illuminates. The presence of a PDTC without an illuminated MIL means that the onboard monitoring system has not yet completed its verification process.

So, how do you diagnose permanent DTC codes? Here are the steps you should follow:

• Check the vehicle's manual:Before you start diagnosing the issue, it's crucial to know the specific error code. You can find this information in the owner's manual of your vehicle.
• Use an OBD scanner:An OBD scanner is a device that reads and interprets the error codes generated by your vehicle's onboard diagnostics system. You can easily connect it to your car's diagnostic port and it'll provide you with a specific error code.
• Inspect the vehicle:Once you have the error code, inspect the vehicle for any visible signs of problems. For example, if the error code indicates a problem with the engine, look for any signs of oil leaks or damaged components.
• Check the vehicle's history:If you've recently had any repairs done on your vehicle, it's essential to check if the issue could be related to those repairs. If so, you should take your vehicle back to the mechanic for further inspection.
• Consult a professional:If you're unable to diagnose the issue on your own, it's always best to consult a professional mechanic. They will have the knowledge and tools to diagnose and repair the problem,

Diagnosing permanent DTC codes requires a systematic approach, and it's crucial to follow the steps outlined above to ensure an accurate diagnosis. If you're unsure about the diagnosis, it's always best to consult a professional mechanic for assistance.

How to Clear Permanent DTC Code

With the right approach, repairing a permanent DTC code is not an impossible task. Here are a few methods to clear a PDTC:

• Method 1: Three Consecutive Confirmed Fault-Free Monitoring Cycles

The first method to clear a PDTC involves allowing the vehicle to run for three consecutive confirmed fault-free monitoring cycles. During these cycles, the vehicle's onboard computer system will run a diagnostic test. If the test runs without identifying any issues, the PDTC will be cleared at the start of the fourth fault-free monitoring cycle. This method requires the vehicle to be driven for a certain amount of time to ensure that the diagnostic test is run correctly.

• Method 2: Clear DTC Request via Scan Tool

The second method to clear a PDTC is to use a scan tool to request a "clear DTC." A scan tool is a diagnostic tool that can be connected to the vehicle's onboard computer system to read and clear DTC codes. This method will clear the PDTC after one confirmed fault-free monitoring cycle following the "clear DTC" request.

• Method 3: Universal Trip Drive Pattern

The third method to clear a PDTC involves performing a Universal Trip Drive Pattern. This is a set of instructions specific to your vehicle, listed in the factory service manual (FSM), that guide you through a series of starting and driving the vehicle at certain speeds and intervals. 

The UTDP is designed to prove to the computer that the fault has been repaired and that no one is trying to cheat on an emissions test. It's important to follow the instructions exactly, as the UTDP is vehicle-specific and not following it correctly could result in the PDTC not being cleared.

Can You Pass a Fog Check Inspection With a Permanent DTC Code?

The Fog Check inspection is a crucial aspect of vehicle maintenance, aimed at reducing harmful emissions and improving air quality. Vehicles that fail this inspection are deemed to have serious problems with their emission control systems, and owners are required to address these issues before they can pass the test.

But what happens when a vehicle has a permanent Diagnostic Trouble Code (PDTC) stored in its On-Board Diagnostic (OBD) system? Can it still pass a Smog Check inspection?

The answer is no, a vehicle with a PDTC stored in its OBD system cannot pass a Fog Check inspection. PDTCs are error codes that indicate a problem with the vehicle's emission control system and are more serious than regular Diagnostic Trouble Codes (DTCs). The use of PDTCs in the Smog Check program ensures that vehicles are operating correctly and not just hiding emission-related problems to pass the test. 

The presence of a PDTC in the OBD system indicates that the vehicle's emission control system is not working correctly. This means that even if the vehicle's malfunction indicator light is not illuminated, the PDTC will cause the vehicle to fail the Smog Check inspection.

Preventing Permanent DTC Codes

Vehicle owners and technicians alike can agree that permanent DTC codes are a frustrating and concerning aspect of modern vehicle technology. These codes are designed to stop individuals from cheating on emission tests by simply clearing the codes without fixing the underlying problem. 

However, this can leave many honest vehicle owners struggling to understand what to do when faced with these codes.

The good news is that preventing permanent DTC codes is fairly straightforward and requires only a little bit of knowledge and effort.

So, how can you prevent permanent DTC codes from affecting your vehicle? Here are a few tips to keep your emissions system running smoothly and avoid costly repairs:

• Regular Maintenance:Regular maintenance of your vehicle, such as regular oil changes, tire rotations, and air filter replacements, can help keep the emissions system running efficiently.
• Use High-Quality Parts:When it comes time to replace parts in your vehicle's emissions system, it's crucial to use high-quality parts that are made for your specific vehicle make and model.
• Avoid Tampering:Tampering with your vehicle's emissions system, such as removing the catalytic converter, can lead to permanent DTC codes. Avoid making any modifications to your vehicle that could impact its emissions.
• Monitor Your Vehicle's Performance:Pay attention to how your vehicle is running and take note of any unusual sounds or changes in performance. If you suspect that there's an issue with your vehicle's emissions system, it's important to get it inspected as soon as possible.

By following these tips, you can avoid costly repairs and ensure that your vehicle is emitting pollutants within legal limits. So, take care of your vehicle and protect the environment, too.

Conclusion

Permanent DTC codes are simply an updated indication of a malfunction in your vehicle. By understanding the root cause, and keeping in mind the purpose of these changes - a more accurate testing process and decreased pollution - you can confidently diagnose and repair these codes. Whether you choose to do it yourself or take it to a professional mechanic, diagnose and repair the underlying issue that triggered the codes in the first place.