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.


Reading measured value block

The following measured values are displayed:

Measured value block 001:  

J Wheel speed front left

J Wheel speed front right

J Wheel speed rear left

J Wheel speed rear right


Measured value block 002:

J Starting speed front left

J Starting speed front right

J Starting speed rear left

J Starting speed rear right

When the vehicle is stopped the tester always displays 255 km/h.


Measured value block 003:

J Brake light switch (tester readout unpressed or pressed)                                                         

J Vacant

J Vacant

J Vacant


Measured value block 007:

JTCS button (possible tester readouts: pressed and unpressed)

J Vacant

J Vacant

J Vacant


Measured value block 125:

JCAN signal from engine control unit

JCAN signal from steering angle sender

JCAN signal from four-wheel drive control unit (quattro vehicles only)

JCAN signal from gearbox control unit (automatic gearbox only)


Measured value block 126:

JCAN signal from dash panel insert

JCAN signal from gateway

JCAN signal from immobilizer

J Vacant


Possible readouts: 1 or 0, (If a 1 is shown on the tester the value is OK; if 0, n.OK.

If a 1 is displayed, a CAN message is sent from the relevant control unit.

  If the tester shows a 0, the CAN message is interrupted.

In such cases read the fault memory of the relevant control unit.


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