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Inspecting charge pressure control solenoid valve N75 > < Checking charge air pressure system

Octavia Mk1

Test charge pressure
Test charge pressure
Special tools and workshop equipment required
t  Vehicle system tester -V.A.G 1552- with cable -V.A.G 1551/3, 3A, 3B oder 3C-
In order to check the function of the charge pressure control, it is necessary to first of all determine the charge pressure without charge pressure control.
Test sequence
   
–  Release plug connection from the solenoid valve for charge air pressure limitation - N75--2-.
–  Measure the charge pressure with the vehicle system tester -V.A.G 1552 - during a test drive.
  WARNING
The -V.A.G 1552- should be operated by a second person.
–  Read measured value block, display group 011, engine at idling speed → Chapter.
–  Accelerate vehicle in 3rd gear at full throttle from about 1500 rpm.
–  At about 3000 rpm read off the value indicated in the display field 3 and note.
  A10-0121
Specified value in display field 3: 1550….1750 mbar
If the measured charge pressure is too low, the following faults are possible:
t  Intake manifold pressure sender defective.
t  Leak between turbocharger and intake manifold.
t  Turbocharger defective (turbine blocked by foreign bodies).
t  Operation (linkage, shaft) of bypass valve stiff or firm (bypass valve always open).
If the measured charge pressure is too high, the following faults are possible:
t  Hose of the charge pressure control released, leaking or clogged.
t  Solenoid valve for charge pressure control -N75- clogged.
t  Operation (linkage, shaft) of bypass valve stiff or firm (bypass valve always open).
t  Pressure box leaking.
If the measured charge pressure is o.k., repeat charge pressure measurement with charge pressure control:
–  Fit on connector at charge pressure control solenoid valve -N75 -.
–  Read measured value block, display group 011, engine at idling speed → Chapter.
–  Accelerate vehicle in 3rd gear at full throttle from about 1500 rpm.
–  At about 3000 rpm read off the value indicated in the display field 3 and note.
For vehicles ? 07.97
  
Reading measured value block 11     ->
3040 rpm   1846 mbar   1693 mbar    39%
Specified value in display field 3: 1750….2150 mbar
For vehicles 08.97 ?
  
Reading measured value block 11     ->
3090 rpm   1866 mbar   1917 mbar    62%
Specified value in display field 3: 1750….2050 mbar
For all vehicles
If the measured charge pressure is too low, the following faults are possible:
t  Charge pressure control solenoid valve not electrically operated.
t  Charge pressure control solenoid valve -N75- jams in the open condition.
If the measured charge pressure is too high, the following faults are possible:
t  Charge pressure control solenoid valve -N75- jams occasionally in the closed condition.
t  Charge pressure increase through "tuning"
  
Reading measured value block 11     ->
3090 rpm   1866 mbar   1917 mbar    62%

Inspecting charge pressure control solenoid valve N75 > < Checking charge air pressure system