Engine Control Unit: The Pivotal Part of a Car

DME ISN Reader
Engine Control unit

Commonly known as ECU to the world, Engine Control Units are machines facilitating great performance of the engine by dominating a whole series of actuators set on an engine which has an internal combustion system. The ECU detects the values from a wide array of sensors that are available. This helps in the successful interpretation of the data and makes use of the multidimensional maps which are called the lookup tables, to be precise. The actuators of the engine are adjusted accordingly.

Your car or any vehicle, for that matter, requires proper controlling of its engine. ECU is considered to be the computer of the car that is the most powerful. The ECU uses a control scheme which is of the closed loop nature. This scheme keeps a check on the outputs of the system in order to estimate how the inputs function. This, in turn, also manages the emissions of the engines as well as its full economy. The ECU basically collects data from a huge number of sensors; hence it has information about the coolant temperature as well as how much oxygen the exhaust contains. After gathering all the necessary data, it performs innumerable calculations in every second which involve checking values from the table, calculating lengthy equations in order to choose which will be the best kind of spark timing and of course, determining the period of time for which the fuel injector is kept open. All these tasks are undertaken by the ECU to ensure that all the aspects of the machine function normally.

The ECU is basically an integral portion of the Electronic Fuel Injection or the EFI which is the most frequent fuel injection system that is being used in cars recently. EFI can be classified into three portions namely, an induction system along with the fuel delivery system as well as the electronic control system.

The most notable functions of a Fuel injection ECU System has been compiled below:

  1. Keeping the air or fuel ration in check:

The particular fuel injection boasts of a number of functions. One of the topmost functions will, however, be its monitoring of the fuel mixture that is being used by the cars. It is the responsibility of the ECU to note the amount of fuel that is inserted into the engine. This particular computer program gets a huge amount of data and computes them properly so that they can be prepared with a decent amount. The ECU delivers air to the engine and determines the air-fuel ratio deftly and consequently, this entire process is called injection duration or even injection pulse width.

  1. Determining the idle speed and controlling it:

The majority of the cars nowadays have a control system which helps in maintaining the idle speed which in turn, is controlled by a throttle stop which is programmable in nature. It also maintains the time of ignition of an engine apart from this. This is done by the ECU effectively by adjusting the right time when the spark plug should be sparked which will, consequently result in improved power.

  1. The valve timing which is variable in nature is also controlled by the ECU. As the flow of the air is increased to the maximum level inside the cylinder, the power, as well as the performance of the car, is enhanced highly.
  2. The data which the ECU sensors collect enables it to monitor the engine’s speed, throttle angle as well as coolant temperature along with the exhaust oxygen content.
  3. The system operation that works for an ECU is by pulsing or even controlling the fuel injections that are present in the engine. The fuel along with air has a particular ratio which is finalized by the amount of air that is taken into the vehicle by its engine as well as the engine’s rpm. The fuel injection sensor signalised the ECU to come up with the right air fuel ratio.

BMW DME Features

The engine control unit in BMW cars is called as DME , it stands for Digital Motor Electronic.

The DME in BMW was designed to have unique features, it has a security associated with CAS ( Car Access System ) to prevent car from being stolen.

BMW depends on on something called ISN  ( Individual Serial number ), this ISN is a secret number (password) known only by the CAS and DME, this ISN is used to Authenticate the BMW key, when 3 parts are verified (DME, CAS, Key), then the engine will start.

The problem starts when a DME get defected, repair shops are forced to order a new DME from BMW, they cannot use another used DME as the ISN will differ from CAS and key, so it wont start.

The average price of a DME from BMW is about $1800, this is a painful price for BMW cars owners.

There is an excellent solution to solve this matter: Autohex II scan tool, it is a special tool that can read ISN from DME and write it into the CAS, so the donor DME will work in the car.

Autohex II scan tool is a well known brand in the BMW repair shops, it can do all the special functions for BMW Ecus from Ecu flashing , Ecu coding, Key programming, and ISN reader.

Repair shops who own Autohex II scan tool, they can buy a DME from the junk yards at about $200-300 only, with the help of Autohex II they can read the ISN from old DME and write it into the new DME (or reading ISN from donor DME and write it into CAS), then flashing the DME to update the internal program inside and code it, then the car is ready for delivery.



BMW, one of the most sought-after brands in cars all over the world, has provisions for programming its keys! Yes, with the advancement of technology, you have many tools and software that can be used for programming the keys to these cars. Let us know more about these BMW Key Programmers.

A BMW key programmer allows the users to read, write, block, unblock, save or delete any CSA key. A BMW key programmer in an all-in-one programmer which is capable of solving different issues related to BMW key programming.

One of the leading BMW key programmers is Autohex II. This brand also produces diagnostic software for BMW. Its main key learning functions are:

  • Managing Current Keys: It enables or disables keys in BMW vehicles.
  • To Program Key in Ignition Shot: It can be used to program transponders in ignition shot.
  • To Program Prepared Key: It can program a prepared key in HTag Pro Key Tool.
  • Program Key when All Working Keys are Lost: It mainly deals with the cars whose all keys are lost in encrypted CAS3, CAS3+ and CAS4.

Here are three key programming methods with respect to BMW Key Programming to try out:

  • Method 1
  • Here you need to work from inside the vehicle with the doors shut.
  • The ignition must be turned to Position1 and it should be turned off after five minutes.
  • The key should be removed from ignition. Next, the unlock button must be pressed and held for about 15 seconds at this time. Within these 15 seconds, the key lock button should be pressed thrice (for duration of five seconds each time).
  • Finally, both the buttons must be released.
  • Method 2

Here two keys are required- one that is working and the other which requires programming.

  • One needs to get inside and close all the doors.
  • The ignition must be turned on and then immediately turned off. It should not take more than five seconds for the purpose. One needs to perform the next action within 30 seconds.
  • The first key should be removed.
  • The key must be held near someone’s left shoulder (in order to keep it closer to the remote receiver antenna).
  • The unlock button must be held down and the lock button must then be pressed thrice. The unlock button and the door lock confirming the operation must then be released.
  • Finally, repeat the above steps for the other keys like Key 2.

Note: You do not know in which order it would work. So, try out both combinations such as Key 1 followed by Key 2 and vice versa.

  • Method 3

People who do not have a working remote may try out this one.

  • You must turn the key to position 1 five times in a very quick manner five times.
  • The key must then be removed.
  • The unlock button must be held and then the lock button must be pressed thrice. Finally, release the unlock button.
  • In case there’s another key, the same button pressing must be done for 30 seconds.

It should be kept in mind that this procedure is applicable for the remote control part of the key. A transponder chip of the immobiliser (the part that is concerned with starting of the car) cannot be done in this way. You need to contact a specialist for the purpose.

For more information related to this field, trust no other company except Microtronik.

So, all the BMW owners out there- enjoy key programming with your car now!