CVN Fix: Everything about Calibration Verification Number!

Reading time 4 Min.

The world of chip tuning has been stumbling ever since Dieselgate (exhaust scandal) again and again about the term CVN or Calibration verification number. But what is actually behind it? To put it simply, the CVN is the result of the combination of three important data sources: the checksum, the Software numbers and the Chassis number. Your main task is to monitor the software statuses during technical reviews, such as Main inspection or directly with the manufacturer. The CVN amends itself, as soon as there is even one value in the engine control maps is modified. This is a direct result of adjustments such as those made in... Chiptuning happen. It quickly becomes clear why the CVN is known in tuning circles as “notorious" applies.

CVN Fix – Explanation

The Adaptation of the CVN, often as "CVN Fix“It is routine for professionals, but it has its pitfalls. Not all Control devices and software versions allow such adjustment, and despite a service that is often free (in combination with chip tuning) the correctness of the CVN cannot always be guaranteed by the tuner. In addition to the CVN, there are others Check numbers in the control unit, which can indicate mods. The CVN review has become particularly important in Germany. Vehicles that have been “chipped” will fail the new one during the general inspection HU adapter occur more frequently. And an incorrect CVN leads to one significant deficiency and in the worst case scenario can lead to the vehicle being shut down.

Why does the CVN actually exist?

The review of the CVN was increased after the exhaust scandal introduced to check whether vehicle owners had the software updates required at the time carried out. Unfortunately that is CVN exam primarily a German phenomenon and plays only a minor role internationally.

Stir through CVN Fix

A “CVN Fix” is carried out by the Adjustment of the data status, so that the original CVN is restored. However, this can be a challenge as many tuners incorrectly assume that flash devices automatically correct the CVN. In reality, however, it is often just a special one Flash device able to do so, and even then only for certain control unit types. And manually adjusting the CVN requires in-depth knowledge and access to manufacturer information, which poses problems for many tuners.

The checksum, a checksum to check the integrity of a data status, plays a crucial role. Any modification of the data status requires a correct adjustment of the checksum. Incorrect checksums can have serious consequences and make the vehicle unusable.

Conclusion: A correct CVN adjustment is essential for vehicles after tuning no unpleasant surprises at TÜV (HU). Despite the complexity and potential risks, the CVN fix is ​​a not entirely unimportant part of chip tuning that requires in-depth knowledge. The industry still struggles with knowledge gaps and misinformation in this area, highlighting the need for experienced professionals.

FAQ: kIs a TÜV with MHD possible for the BMW?

• MHD tuning is a popular method for giving BMWs better performance. But be careful: this is not always legal!
• Within the HU it can get tricky. Modern testing centers check the Calibration Verification Number (CVN), which reveals whether the engine control unit has been messed with.
• CVN fix? Yes, there are ways to adjust the CVN to match the original again. But: That doesn't make it legal.
  – Back to series: Before you drive to the HU, flash your car back to the original software back. This is the safest way to get through the HU without any problems.
  – Exceptions: If you have activated certain features via MHD (such as the OPF delete or the control of the exhaust flap), you have to get creative. There are solutions, but simple is different.

• CVN definition: Abbreviation for Calibration-Verification-Number, based on checksum, Software numbers, Chassis number.
• Purpose of the CVN: Checking software versions at TÜV and manufacturers.
• CVN variability: Changes with every update of the engine control maps.
• CVN Fix: Adaptation of the CVN is standard for chip tuning; not always possible, depending on the control unit and software version.
• Importance of CVN: Often neglected, but crucial for TÜV tests in Germany.
• Test numbers in the control unit: Indicate chip tuning and potential manipulation.
• TÜV failure rate: Increases due to CVN testing, especially on modified vehicles.
• CVN exam: Originally introduced after emissions scandal; checks implementation of software updates.
• Affected vehicles: Mostly German brands and vehicles from 2010; EDC17 control units and some EDC16 as well as foreign manufacturers.
• Adaptation of the CVN: Manually by experienced professionals; Automatic correction using flash devices is only partially possible.
• Problems with CVN Fix: Many tuners have insufficient knowledge; only one flash device on the market can automatically adjust CVN for specific ECUs.
• checksum: Essential for the integrity of a data set; incorrect adjustment can lead to vehicle failure.
• Conclusion: Proper CVN fitting requires in-depth expertise; large knowledge gaps in the industry

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