There are many "myths" and misunderstandings about BMW ECU / DME reprogramming. We hope to help answer and give you solutions to the most commonly asked questions.
My mechanic/dealership says that you can’t reprogram, re-code, or swap a used BMW ECU between cars. How can you help me?
This is true, but we have the solution!
Ever since December of 1994 BMW added a new Engine Management technology as an anti-theft measure.
The new anti-theft technology is a device called the "EWS", which is also known as the "Immobilizer". This module compares the VIN number of the car between different electronic modules in the car. If the VIN number isn't consistent, the car will not start.
Also the EWS has a password feature called the "Rolling Code" which changes between the modules every time that the car is turned off. This makes it virtually impossible to swap used ECU's between BMW cars.
However, we’ve found a way to work around this.
We can reprogram a used ECU using another VIN number and reset the Rolling Code, virtually making the unit "virgin". Only then, can we successfully exchange and swap a used ECU to work in another BMW car. All you need to do is align our ECU to your car's EWS using this USB Interface Cable Car with you laptop USB connection and the car's OBD2 Diagnostic terminal.
Why can’t I buy a used BMW ECU online and install into my car myself?
Because if you install a used ECU in any BMW, the VIN number and Rolling Code will not match, and it will prevent the car from starting.
The EWS was created for this very purpose. What happens is that the EWS system connects with the key transponder, but fails to properly communicate with the DME. The car might crank, but the DME will never get the "permission" to power the fuel pump and send the spark signals.
When I buy an Exchange BMW DME from you, will the unit be Plug and Play?
Our Exchange ECU's are programmed to your BMW's VIN number.
However, due to the fact that the EWS systems have a random "Rolling Code" we can't guess this code.
Therefore, we reset this feature in order to make the ECU "blank".
In order for the unit to work in the car, a DME to EWS Alignment/Synchronization has to be carried out.
This is done using a BMW scanner like this USB Interface Cable Car with you laptop USB connection, a GT1, ISTA, Autologic, Launch X431 or Baum Tool DS2021. It takes 5 minutes to "marry" the ECU to your car, and then the ECU is ready to start the car.
If you Repair my ECU, do you I need to “re-flash”, "re-code" or “re-program” the ECU before installing back into my car?
No. ECU re-programming is not required because most repairs are done on the hardware parts and not on the software programming. Therefore, the programming of the ECU will never be altered.
Every mechanic and dealership will often use different words and terms to explain to you how ECU's and scanners work, which can be confusing.
Here is a quick "definitions guide" to help you understand them better:
- BMW Scanner: They are used to scan all the electronic modules in the car to find out what may be causing a Check Engine Light to come on, or to define fault codes found in the modules to figure out, and to install software updates on the electronic modules of the vehicle.
- DME ECU Programming: This is the same as when you install the the Windows Operating System in your desktop computer. This process tells the DME to which car it will installed in and how it should manage the engine performance while the car is working. The reprogramming process takes an average of 45 minutes to 1 hour.
- DME ECU Recoding: This process sets on the ECU the VIN number, programming codes, and transmission settings. Many times this process is done together with the ECU Programming.
- DME Alignment/Synchronizing: This is a simple "Copy & Paste" process which takes only 5 minutes. The BMW Scanner copies the "Rolling Code" from the EWS and Pastes it in the DME memory. This process "marries" a new ECU to the vehicle allowing it to start.
These are some OBD2 BMW scanner tools that we recommend to begin diagnosing your own car:
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