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Engine control unit: replace, code and adapt > < Speed signal: check

Leon Mk2

Final resiatance for the data bus: check
Final resiatance for the data bus: check
Working
The engine control unit communicates through a CAN-bus with all the control units prepared for the data bus.
These control units prepared for the data bus are interconnected by means of two data bus cables twisted together, (CAN_High and CAN_Low) and exchange information (messages). The lack of information in the data bus is interpreted as a failure by the engine control unit and the other control units interconnected by means of the CAN data bus.
For problem and parasite free working, the CAN data bus requires a final resistance of 120 Ω. This is found in the engine control unit.
Checking condition
l  The CAN data bus self-diagnosis has detected a fault.
Special tools and workshop equipment required
t  Manual multimeter -V.A.G 1526 A- or multimeter -V.A.G 1715-
t  Auxiliary measuring set -V.A.G 1594 C-
t  Current circuit diagrams
Checking process
–  Turn off the ignition.
–  Unblock the connectors of the engine control unit and remove.
–  Check the central final resistance built into the engine control unit by using the auxiliary cables of the -V.A.G 1594 C-.
   
–  To this effect, measure the resistance between contacts 68+75.
   Theoretical value: 115...135 Ω
If the resistance value fails to lie in the tolerance margin:
–  Replace the engine control unit -J248- → Chapter.
If the resistance value lies within the tolerance margin:
–  Using the circuit diagram, check the cables to the components of the CAN data bus for short circuit to positive or ground or breakage → Current flow diagrams, Electrical fault finding and Fitting locations.
  E23-0040

Engine control unit: replace, code and adapt > < Speed signal: check