Boost pressure regulation, checking

Special tools, testers and auxiliary items required 

• Fault Read Out Device V.A.G 1551 or Vehicle Diagnosis, Testing and Information System VAS 5051

Test conditions 

• There must be no malfunctions stored in DTC memory.
• No leaks on intake or exhaust side.
• Engine oil temperature at least 80 ° C

Test sequence 

• Charge pressure is measured under Wide Open Throttle (WOT) while driving or on the roller type test stand.

Observe safety precautions that apply to road tests refer to Safety precautions  .

• Connect Fault Read Out Device V.A.G 1551 and select engine electronics control module with "Address word 01". Engine must run at idle for this. Connect fault read out device and select engine control module.

Scan tool display:

Quick data transfer HELP Select function XX

• Press buttons 0 and 8 for function "Reading measuring value blocks" and press Q button to confirm input.

Scan tool display:

Read measuring value block Enter display group number XXX

• Press buttons 1 1 and 4 for the "Display group number 114" and press Q button to confirm input.

Scan tool display: (1 to 4 = display fields)

Read measured value block 114 -> 1 2 3 4

• During a road test or on a test stand, check (at full throttle between 1800 and 2300 RPM) duty cycle of Wastegate Bypass Regulator Valve N75 in display field 4. Specified value: 5.0 to 95.0%

If specified value is not achieved:

• Switch to display group 15 as follows: Press 3 button.

Scan tool display: (1 to 4 = display fields)

Read measured value block 115 -> 1 2 3 4

• Check charge air pressure actual value with wide open throttle (WOT) in display field 4:

While driving 

Vehicles with manual transmission

• Accelerate vehicle at Wide Open Throttle (WOT) in 2nd gear.

Vehicles with automatic transmission

• Manually shift vehicle in 4th gear and accelerate vehicle from low speed at Wide Open Throttle (without kick down, transmission does not downshift any more).

Engine code AWD, AWW 

• Press print button between 1800 and 2300 RPM and read out charge air pressure actual value in display field 4. Specified value: 1350 to 1750 mbar

Engine code AWP 

• Press print button between 1800 and 2300 RPM and read out charge air press actual value in display field 4. Specified value: 1700 to 2000 mbar

Continuation for all vehicles 

• Compare charge air pressure actual value with specified value in display field 3. Difference: max. 100 mbar

• Press → key.
• Press buttons 0 and 6 for function "End output" and press Q button to confirm input.
• Switch off ignition.

If boost pressure is exceeded:

• Test the Charge Air Pressure Sensor G31 refer to Charge Air Pressure Sensor G31 , checking  .
• Check Wastegate Bypass Regulator Valve N75. (Throughput in hose from turbocharger via valve to vacuum diaphragm with connector disconnected)
• Check that vacuum diaphragm for charge pressure regulator valve is securely seated on turbocharger.
• Check vacuum diaphragm, refer to Vacuum diaphragm for boost pressure regulator valve, checking  .

• Check the mounting of the boost pressure regulator valve shaft in the turbocharger for ease of movement. If rusted in place, replace turbocharger.

If boost pressure is exceeded:

• Test Charge Air Pressure Sensor G31 refer to Charge Air Pressure Sensor G31 , checking  .
• Check Wastegate Bypass Regulator Valve N75.
• Check mounting of the boost pressure regulator valve shaft in the turbocharger for ease of movement. If rusted in place, replace turbocharger.
• Exhaust turbocharger faulty, replace it, refer to Turbocharger with attachments, assembly overview  .

• Check DTC memory.
• Read readiness code.
• If DTC memory was cleared or engine control module disconnected from voltage supply, readiness code must be regenerated.