ECU - Electronic Control Unit

In terminology of VW-group it's any electronic device, which has been carried out some logic function. Sometimes it looks like nonsens - even simple relay can be called ECU.

The coding of Electronic Control Unit used for explain the ECU where it is and what "neighbours" does it have. Very often on modern cars the coding is crossed with adaptation.

Adaptation of the Electronic Control Unit serves to explain to the ECU with whom and how to talk (If we have started to speak allegories) and serves as storehouse of various adjustable parameters. ( part of memory in the Control Unit which can be changed via internal software )

Measured Values Blocks ( MWB ) – various parameters being inbound or calculated. Considering to value of MWB Electronic Control Unit, trying to "control"... Using of MWB allows you ( if you know the basic parameters ) to find out "close to boundary" or temporarily arising ( intermittent, sporadic ) malfunctions and many other useful things at competent use.


The throttle valve control part must be adapted to the engine control unit -J220 when:


1. the voltage supply to the engine control unit -J220 has been cut.


2. the throttle valve control part  -J338 has been removed and reinstalled or replaced.


3. the engine control unit -J220 has been replaced.


4. a different throttle control part has been fitted as a result of fitting of a different engine.



By the adaption, the engine control unit learns various positions of the throttle valve with the ignition switched on and the engine off. These positions are stored in the control unit. The checkback of the throttle valve position is transmitted by way of the two angle senders for throttle valve drive.


The adaption is carried out:


J by initiating basic setting (function 04), display group 60 with the ignition on.


J automatically if the ignition is switched on for at least 6 seconds without operating the starter and accelerator pedal and if the engine control unit detects a learning requirement. (This gives no indication, however, of whether the adaption was successful or not). A learning requirement is detected when stored voltage values from the angle senders do not match current measured voltage values within a certain tolerance range.



What happens during adaption?           


First the power is cut to the throttle valve adjuster. The throttle valve is then drawn to an emergency running position by a mechanical spring located in the throttle valve control part. The values delivered by the two angle senders in this emergency running position are stored by the engine control unit.


Then the throttle valve is opened by a specific value. When this value is reached, power is cut to the throttle valve adjuster. Then the mechanical spring must close the throttle valve within a specific time as far as the previously taught-in emergency running position (spring test).

Then the throttle valve is closed by the throttle valve adjuster. The values delivered by the two angle senders in the throttle valve control part are stored in the engine control unit.



If the engine control unit cuts the power to the throttle valve adjuster while the vehicle is running, the symptom is an increased, surging idling speed. The engine picks up the throttle only after a substantial delay.


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