Turbocharger: Testing and Inspection

Boost pressure system, checking
Boost pressure regulation, checking
Special tools and equipment
^ VAG1551 scan tool (or VAG1552 mobile scan tool) with VAG1551/3 cable

Test requirements
^ No leaks on intake or exhaust side.
^ Engine oil temperature at least 80°C

Test sequence
- Connect VAG 1551 scan tool (VAG 1552). Start engine and select the Engine Control Module (ECM) using address word 01. Connecting scan tool and selecting Engine Control Module (ECM):





Indicated on display:
- Press buttons -0- and -8- to select "Read measuring value block" function 08. Press -Q-button to confirm input.





Indicated on display:
- Press buttons -1-, -1- and -4- to select "display group number 114" and then press -Q-button to confirm input.





Indicated on display
- Check duty cycle of wastegate bypass regulator valve during a road test or on a chassis dynamometer (at Wide Open Throttle between 1800 and 2300 RPM) in display field 4.
Specification: 5 to 95%

If specified value is obtained:
- Press -C-button.
- Press buttons -1-, -1- and -5- to select "display group number 115" and then press -Q-button to confirm input.





Indicated on display
- Check actual charge pressure value in display field 4 at Wide Open Throttle (WOT):

On dynamometer
In 3rd gear or in 2nd drive mode

While driving
Vehicles with manual transmission
- Accelerate vehicle at Wide Open Throttle (WOT) in 2nd gear

Vehicles with automatic transmission
- Manually (Tiptronic) place vehicle in 4th gear and accelerate vehicle from low speed at Wide Open Throttle (without kick down, transmission does not downshift any more).
- Press print button between 1800 and 2300 RPM and check actual boost pressure value in display field 4.
Specification: 1350 to 1750 mbar
- Compare actual boost pressure with specification in display field 3.
Difference: maximum 100 mbar

Note: Repeat measurement if boost pressure was not fully charged or if the difference between actual and specified values was too large.

If boost pressure is exceeded:
- Check charge air pressure sensor -G31-, Refer to Turbo Boost Sensor.
- Check wastegate bypass regulator valve -N75-. (Throughput in hose from turbocharger via valve to vacuum diaphragm with connector disconnected)
- Check for proper seating of vacuum diaphragm for wastegate bypass regulator valve at turbocharger.
- Check vacuum diaphragm
- Check bearing for shaft of wastegate bypass regulator valve in turbocharger for ease of movement. If rusted solid, replace turbocharger.
If boost pressure is not reached:
- Check charge air pressure sensor -G31-
- Check wastegate bypass regulator valve -N75-.
- Check bearing for shaft of wastegate bypass regulator valve in turbocharger for ease of movement. If rusted solid, replace turbocharger.
- Turbocharger faulty, replace.