With Manufacturer's Scan Tool
Charge Air Pressure Regulation, Checking
Special tools and equipment
- VAG 1551 Scan Tool
NOTE: The vehicle system tester VAG 1552 can be used instead of the VAG 1551 scan tool, however a print-out is not possible.
- VAG 1551/3 Cable
Check conditions
- DTCs must be stored in DTC memory:
- No leaks on intake and exhaust systems.
- Engine oil temperature min. 80 degrees C
Test sequence
The charge air pressure is measured under full load, while driving or on a rolling road.
Observe applicable safety precautions when performing a road test.
- Connect VAG 1551 Scan Tool (or VAG 1552). Start engine and select engine electronics control module with "Address word" 01.
Indicated on display
Rapid data transfer HELP
Select function XX
- Press keys 0 and 8 for function "Read measured value block" and confirm entry with Q key.
Indicated on display
Read measured value block
Input display group number XXX
- Press keys 1, 1 and 4 for "Display group number 114" and confirm entry with Q key.
Indicated on display: (1 to 4 = Display zones) 1
Read measured value block 114
1 2 3 4
- Check duty cycle of Wastegate bypass regulator valve -N75- in display zone 4 (at Wide Open Throttle between 1800 to 2300 RPM) during a test drive or on a rolling road.
Specification: 5.0 to 95.0%
If the specification is obtained:
- Change to display group 115 as follows: on VAG 1551: Press key 3; on VAG 1552: Press key up-arrow
Indicated on display: (1 to 4 = Display zones)
Read measured value block 115
1 2 3 4
- Check charge air pressure (actual value) at Wide Open Throttle (WOT) in display zone 4:
On rolling road
- In 3rd gear or in 2nd driving range
During test drive
Vehicles with manual transmission
- Accelerate in 2nd gear with Wide Open Throttle (WOT).
Vehicles with automatic transmission.
- Manually select drive mode 4 (Tiptronic) and accelerate vehicle from a low speed at Wide Open Throttle (WOT), without Kick-Down (transmission no longer shifts down).
Engine speed AWD, AWW
- Press print button between 1800 to 2300 RPM and read charge air pressure actual value in display zone 4.
Specification: 1350 to 1750 mbar
Engine speed AWP
- Press print button between 1800 to 2300 RPM and read charge air pressure actual value in display zone 4.
Specification: 1700 to 2000 mbar
Continued for all vehicles
- Compare actual charge air pressure value with specified charge air pressure value in display zone 3.
Difference: max. 100 mbar
NOTE: Repeat the measurement if the charge air pressure has not fully built-up or there is a large difference between specified and actual values.
- Press -> key.
- Press keys 0 and 6 for "End output" function and confirm input with the Q key.
- Switch ignition off.
If the charge air pressure is exceeded:
- Check Charge air pressure sensor -G31-. Testing and Inspection
- Test Wastegate bypass regulator valve -N75-. (Hose from turbocharger via valve to pressure unit not blocked when connector is pulled off).
- Check pressure unit for charge air pressure regulating valve is securely mounted on turbocharger.
- Check pressure unit.
- Check shaft mount for charge air pressure regulating valve in turbocharger for ease of movement. When corroded together, replace turbocharger.
If the charge air pressure is not attained:
- Check Charge air pressure sensor -G31-. Testing and Inspection
- Check Wastegate bypass regulator valve -N75-.
- Check shaft mount for charge air pressure regulating valve in turbocharger for ease of movement. When corroded together, replace turbocharger.
- If turbocharger is faulty, replace turbocharger.
- Check DTC memory.
- Read readiness code.
- Generate readiness code again if DTC memory has been erased or engine control module separated from permanent positive.