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Checking knock sensors > < Checking control unit power supply

A3 Mk1

Checking knock control limit
Checking knock control limit
Perform the following checks if a fault entry relating to “Knock control limit reached” has been stored.
–  Connect up the vehicle diagnostic and service information system -VAS 5052- and select the engine electronics control unit. Engine must be idling.
–  Select the function “Read measured value block”.
–  Select “Display group number 020”.
–  Check the display in all zones.
   
 Display zones
 1234
Display group 020: Ignition - knock control whilst driving
Displayxx.x °crank anglexx.x °crank anglexx.x °crank anglexx.x °crank angle
DisplayIgnition timing retardation, cylinder 1 due to
knock control		Ignition timing retardation, cylinder 2 due to
knock control		Ignition timing retardation, cylinder 3 due to
knock control		Ignition timing retardation, cylinder 4 due to
knock control
Specification0...12 °crank angle0...12 °crank angle0...12 °crank angle0...12 °crank angle
NoteSee evaluation

  Note
The numerical values displayed in zones 1 to 4 represent the actual ignition timing retardation by the knock control for the individual cylinders. The ignition timing is retarded in ° crank angle.
Evaluation of ignition timing retardation
   
Indicated on displayPossible cause of troubleRemedy
All cylinders greater than 12 °crank angle
t  Knock sensor defective
–  Check the knock sensor → Chapter
 
t  Connector corroded
 
 
t  Knock sensor incorrectly tightened
–  Slacken knock sensors and tighten to 20 Nm
 
t  Engine attachments loose
–  Secure the attachments
 
t  Poor fuel grade
–  Change to a different fuel grade (refer to owner's manual)
One cylinder deviates significantly from the others
t  Connector corroded
–  Check the knock sensor → Chapter
 
t  Mechanical engine fault
–  Check the compression:
 
t  Engine attachments loose
–  Secure the attachments

   

Checking knock sensors > < Checking control unit power supply