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Testing the engine operating conditions > < Replacing engine control unit

Octavia Mk1

Testing idling speed
Testing idling speed
Special tools and workshop equipment required
t  Vehicle system tester -V.A.G 1552- with cable -V.A.G 1551/3-
Test conditions
l  Exhaust system shut.
l  Coolant temperature minimum 80 °C.
l  Electrical consumers must be disconnected (the radiator cooling fan must be off during this test).
  Note
t  The idling speed cannot be adjusted.
t  The idling speed is checked during the basic setting of the engine.
t  During the basic setting, the activated charcoal filter solenoid valve 1 -N80- is closed and the air conditioning compressor is deactivated.
Test sequence
–  Connect vehicle system tester -V.A.G 1552- and select engine electronics (address word 01); engine runs in idle → Chapter.
–  Interrogate the fault memory → Chapter. There must not be any fault stored, if necessary rectify any fault, erase fault memory, switch off engine and start again, conduct test drive and interrogate the fault memory again for inspection.
–  Keep running engine at idling speed.
  WARNING
The radiator cooling fan must be off.
   
Readout on display:
–  Enter 04 for the function “Initiate basic setting” and confirm with the Q key.
–  Enter “056” for the “display group 056” and confirm entry with the Q key.
  
Vehicle system test                 HELP
Select function XX
Readout on display:
–  Check whether the actual engine speed shown in display field 1 (actual speed) is within the permissible tolerance range of display field 2 (nominal speed).
  Note
t  The speed in display field 1 (actual speed) is indeed the actual engine speed.
t  The speed in display field 2 (nominal speed) is the theoretical speed calculated by the engine control unit.
t  In idle the engine control unit always attempts to adapt the (actual) speed to the specified speed (nominal).
t  This means that engine speed when idling (actual) should always be approximately the same as the engine speed (specified).
t  Display fields 3 and 4 serve as information and are not relevant for the inspection of the idling speed.
If the specified value is reached:
–  Press → key.
  
System in basic setting 56            ->
780/rpm     800/rpm      2.5 %     00000
Read-out on display (function selection):
If the specified value is not reached:
–  Interrogate the fault memory again → Chapter.
If the idling speed is too high or too low, perform the following inspections marked with a point:
t  Inspect unmetered air in the intake system → Chapter.
t  Inspecting throttle valve control unit → Chapter.
t  Check if the activated charcoal filter solenoid valve 1 -N80- is always open → Chapter.
t  Perform adaptation of the throttle valve control unit → Chapter.
  
Vehicle system test                 HELP
Select function XX

Testing the engine operating conditions > < Replacing engine control unit