DTC OFF; A Complete guide

But what exactly are DTCs (Diagnostic Trouble Codes) and why do they appear? Which categories of them can be cleared from the ECU (Engine Control Unit)? How should the DTCs that can be cleared be removed? What are the DTC delete tools? In general, how many types of DTCs are there?

These are questions that may arise if you are a vehicle owner or a workshop owner. In this article, we have tried to answer these questions to serve as a short yet concise and useful guide for you.

What is a DTC?

According to the SAE J2012 standard, a combination of letters and numbers was formed to identify performance issues in vehicles, so that these numbers would become a universal standard worldwide. In this way, according to this standard, any company, mechanic, or vehicle owner can identify the vehicle's problem by seeing these numbers. This specific arrangement or code is called a DTC.

If you still haven't fully understood, wait! Let’s categorize the fault codes into two general categories so we can explain more thoroughly and accurately. DTCs are generally divided into two categories: Generic and Extended. But what is the difference between them?

Extended DTCs:

Extended DTCs are a category of DTCs that are used by the manufacturers of the vehicle or ECU themselves. For example, 180101. This code is a specific extended code for BMW, which means "Catalytic Converter: Efficiency below the limit value." If you pay attention, unlike generic codes that are four digits, this one consists of six digits. The guidelines and lists of extended codes for each company are accessible all over the web. There are also some diagnostic devices specific to each brand that display DTCs in an extended format to the user.

Generic DTCs:

Generic DTCs are designed so that the corresponding fault codes can be translated and referenced by specialists across all brands and ECUs. In the generic case, DTCs start with one of these four letters: P, C, U, and B. B stands for "Body," C is an abbreviation for "Chassis," U stands for "Undefined," and P means "Powertrain." After the letter, there are four numbers in hexadecimal format, which can range from 0 to 9 and then from A to F, such as code C052B, which means "ABS Pump Motor Control Range/Performance."

For more examples, we can refer to well-known codes like P0420 and P0137, where the former means "Catalyst System Efficiency Below Threshold" and the latter means "O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)."

DTC Removal: Which DTCs Can Be removed from the ECU?

One of the questions we are frequently asked is which DTCs can be cleared.

To answer, we must first mention that DTCs removed from the ECU, if done correctly, will be permanently deleted. However, if this is done using a diagnostic device, it will not be permanent. Nevertheless, it is important to note that in any case, you should take DTCs and the check engine light seriously, as there may be a serious issue with your vehicle. In such cases, deleting the DTC, whether through a diagnostic tool or remapping, will not resolve the problem.

Now, keeping this in mind, you should know that only DTCs that start with the letter P (P codes) can be removed from the ECU through remapping, and this option does not exist for the other three letters (B, C and U).

DTC Off Software:

If you want to grapple with the world of fault codes, addresses, and numbers yourself and delete them, you should do this using ECU tuning software like WinOLS and StageX, as these softwares give you direct access to the ECU numbers and maps. However, in other software like ECM Titanium or RaceEvo, you do not have such access.

There are also other software options like Swiftc that automatically perform DTC deletion for certain ECUs.

Which Types of DTCs Can be Deleted?

If we want to rephrase this question, we should ask, "For DTC removal, do we need extended codes or generic ones?" The answer depends on the type of ECU in the vehicle and the working method of your tuner. For example, our method entails that for some ECUs, like TRW, we need the standard extended codes from the manufacturer (Volvo), which are in the form of a 6-digit decimal number. However, for ECUs like Bosch, we require generic DTCs.

Regarding software that automatically removes DTCs, it also depends on the specific software whether it requires generic or extended DTCs. Although in some software, there may be no difference in this regard, and in fact, deletions can be performed with either of these two types of DTCs.

ECU Tuning Tools for DTC Removal:

Many ECU tuning tool manufacturers, such as the Alientech company, AutoTuner, and Flex by Magic Motorsport, have added error code deletion to their programmers. If you have any of these programmers, you can use their DTC delete service by paying the relevant fees (even if they may not match the accuracy of software!).

What is P0000?

P0000, which some tuners refer to as a "Pass code", is often not an actual DTC. In many cases, some diagnostic devices display the message "No error detected" after detecting this code.

The reason for such a fault being shown by your vehicle's diagnostic device can be attributed to several factors.

One possibility is that your diagnostic device is counterfeit or incompatible with the vehicle. Another factor could be that you started your vehicle after performing ECU tuning or after work or repairs on the vehicle's electrical system, which may have caused the ECU to reset, not allowing enough time to fully recover and detect any potential error codes. Additionally, keep in mind that when you have such a code, it is most likely that there are no actual DTCs present.

Solution for P0000 Delete:

Based on the explanation in the previous paragraph, the first step in addressing the P0000 fault is to check for other DTCs that may have appeared simultaneously with this fault. If there are other DTCs along with this one, the best solution is to first delete the other DTCs, as resolving the issues with those DTCs may also resolve the P0000 fault. However, if you do not have any other codes besides P0000, or if you had another DTC that you have resolved and still have P0000, the next step is to consider "driving" your vehicle! Yes, just drive it! The reason for this is that if, as mentioned, the ECU is not detecting DTCs correctly after a reset, driving the vehicle will allow the ECU to gradually detect any DTCs (if they exist). After doing all of this, your issue is likely to be resolved, but if it is still not resolved, you may want to consider diagnosing the vehicle with a better and more reliable diagnostic device.

If you have tried all of this and still have the same issue, we have another solution for you!

Whether you are a tuner or a vehicle owner, if you have deleted the DTCs in the WinOLS software yourself, it’s better to run the original file and the modified file in WinOLS again. Then, by comparing these two files in the WinOLS software, if you used FF to delete the error code area, change it to 00, and if you used 00, change it to FF. What does this mean?

This means that if, for example, you have turned off a P0430 DTC in the WinOLS software and encountered a P0000 DTC, and you have also set the corresponding area numbers in the vehicle dump to FF, this time do it with 00. After saving the new file, rewrite it to your vehicle. There is a very high probability that this time, by doing this, the P0000 DTC will be removed.

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