Charge Air Pressure System, Checking
Charge air pressure regulation, checking
Only engine codes APH
Special tools and equipment
- VAG 1397 A Turbocharger tester
Check conditions
- No leaks on intake and exhaust systems
- Engine oil temperature min. 60°C
Test sequence
Measure the charge pressure under full load, while driving or on a rolling road. Test duration per measurement max. 10 seconds.
- Pull off connecting hose running between intake manifold and fuel pressure regulator at intake manifold and connect in turbocharger tester VAG 1397 A using T-piece.
- Select measuring range -1-.
Note:
- Refer to turbocharger tester operating instructions.
- The hoses must be connected so that there is no possibility of leaks.
- If charge pressure is measured while driving, it is necessary (for safety reasons) for a second person to operate the turbocharger tester.
- Ensure that the pressure hose is not trapped between the hood and the body.
Measuring charge pressure at wide open throttle:
- Accelerate with wide open throttle from 2000 RPM in 3rd gear or in 2nd driving range.
- At 3000 RPM press memory button "M" on turbocharger tester.
Specification: (absolute pressure) 1.300-1.400 bar
If the charge pressure is exceeded:
- Disconnect connector -2- from Wastegate Bypass Regulator Valve -N75- -1-.
- Check hose from connecting pipe (between turbocharger and charge air cooler) via valve to vacuum diaphragm for clogging.
- Check that pressure unit for charge pressure regulator valve is securely mounted on turbocharger.
- Check shaft mount for regulator valve in turbocharger for ease of movement. When corroded together, replace turbocharger.
If the charge pressure is not attained:
- Check Wastegate Bypass Regulator Valve -N75-.
Engine codes: AWP, AWV
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 1551/3B Cable
Test conditions
- Check and erase DTC memory, if necessary:
- No leaks on intake and exhaust systems
- Engine oil temperature min. 80°C
Test sequence
The charge air pressure is measured under full load, while driving or on a rolling road.
Observe applicable safety precautions when carrying out a road test.
- Connect VAG 1551 Scan Tool ((VAG 1552). Start engine and select engine electronics control module with "Address word" 01. Connecting scan tool and selecting engine control module; Connecting VAG 1551 Scan Tool and selecting engine electronics control module
Indicated on display:
- Press buttons -0- and -8- for function "Read measured value block" and confirm entry with -Q- button.
Indicated on display:
- Press buttons -1-, -1- and -4- for "Display group number 1 14" and confirm entry with -Q- button.
Indicated on display: (1 to 4 = Display zones)
- 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...95.0 %
If the specification is obtained:
- Change to display group 115 as follows:
VAG 1551: Press button 3
VAG 1552: Press "up arrow" button
Indicated on display: (1 to 4 = Display zones)
- Check charge pressure (actual value) at wide open throttle 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.
Vehicles with automatic transmission.
- Manually select drive mode 3 and accelerate vehicle from a low speed at Wide Open Throttle (WOT, without Kick-Down).
Engine code AWV
- Press print button between 1800 to 2300 RPM and read charge air pressure actual value in display zone 4.
Specification: 1350 to 1750 bar
Engine code AWP
- Press print button between 1800 to 2300 RPM and read charge air pressure actual value in display zone 4.
Specification: 1700 to 2000 bar
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 -> button.
- Press buttons -0- and -6- for "End output" function and confirm input with -Q- button.
- Switch ignition off.
If the charge air pressure is exceeded:
- Check Charge Air Pressure Sensor.
- Check 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.
- 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.
- Turbocharger malfunctioning. Replace turbocharger
- Check DTC memory
- Read readiness code
If the DTC memory has been erased or the engine control module separated from the permanent positive, the readiness code must be generated again.