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Testing databus (CAN bus) > < Testing auxiliary signals

Octavia Mk1

Testing signals from the air conditioning system
Testing signals from the air conditioning system
The air conditioning system is connected to the engine control unit -J248- via the data BUS. All signals of the air conditioning system to or from the engine control unit -J248- to the air conditioning system are transmitted via the data BUS.
Testing occurs via the measured value blocks of the air conditioning system and engine control unit -J248-.
Special tools and workshop equipment required
t  Vehicle system tester -V.A.G 1552-
t  Diagnostic cable -V.A.G 1551/3- or -V.A.G 1551/3A- or -V.A.G 1551/3B-
Test condition
l  No data bus fault → Electrical System; Rep. Gr.90
Test sequence
–  Connect vehicle system tester -V.A.G 1552-. Start engine and select “address word” 01 Engine electronics → Chapter.
–  Select function 08 “read measured value block” and display group number 002.
   
–  Readout on display:
Air conditioning switched off.
–  Observe display field 3.
   Specified value: 0 1 0
–  Switch on the air conditioning system.
–  Observe display field 3.
   Specified value: 1 1 1
  
Reading measured value block         2   ->
900 rpm       0.0%      111       90.0°C
Meaning, if display positions = 1 
X  XXOperating position 
    1Air conditioning switched on 
   1 Idling switch closed (accelerator pedal not pressed)
1    Speed increase with AC system on

–  Switch off air conditioning again.
–  If the display does not occur as described:
–  Testing air conditioning system → Heating, Air conditioning; Rep. Gr.01.
–  Test data BUS → Electrical system; Rep. Gr.90.
   

Testing databus (CAN bus) > < Testing auxiliary signals