Charge pressure control (Turbo), checking
Charge pressure control (Turbo), checking
Special tools and equipment
^ V.A.G 1551 Scan Tool or vehicle system tester V.A.G 1552 with cable V.A.G 1551/3
Engine Code AEB
^ V.A.G 1397 A Turbocharger tester
Checking conditions
^ No leaks on intake and exhaust systems.
^ Engine oil temperature min. 80° C
Test sequence
- Connect V.A.G 1551 (V.A.G 1552). Start engine and select engine electronics control module with "Address word" 01.
Refer to Powertrain Management.
Indicated on display
- Press -0- and -8- buttons to select "Read measured value block" and confirm entry with -Q- button.
Indicated on display
- Press -1-, -1- and -4- buttons for "Display group number 114" and confirm entry with -Q- button.
Indicated on Display
- Check on/off ratio of Wastegate Bypass Regulator valve -N75- during a test drive or on a rolling test stand (at Wide Open Throttle 1800 to 2300 rpm) in display field 4.
^ Specification: 5 to 95 %
If the specification is obtained: Go to Engine Code ATW
Engine Code AEB
The Charge pressure is measured under full load while driving or on a rolling test stand. Test period per measurement = Max. 10 seconds.
- Disconnect hose between intake manifold and recirculating valve for turbocharger at intake manifold and connect turbocharger tester V.A.G. 1397 A using T piece.
- Select measuring range I.
Note:
^ To operate turbocharger tester see operating instructions.
^ The hoses must be connected so that there is no possibility of leaks.
^ If boost pressure is measured while driving, for safety reasons a second person must operate the turbocharger tester.
^ Ensure that the pressure hose is not trapped between the hood and the body.
- Measure charge pressure at Wide Open Throttle.
On a rolling test stand
Test in 3rd gear (manual transmission), 2nd gear (automatic transmission).
During test drive
Vehicles with manual transmission
- Accelerate vehicle in 2nd gear at Wide Open Throttle.
Vehicles with automatic transmission
- Manually select 4th gear range and begin accelerating from low speed at wide open throttle (avoid kickdown; transmission must not shift into lower gear).
- At engine speed of 1800 to 2300 rpm press memory button "M" on turbocharger tester (V.A.G. 1397 A) and read display.
- Specification: (absolute pressure) 1.350 to 1.750 bar.
Note:
If the full charge pressure was not attained, repeat the test.
If the charge pressure is exceeded:
- 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 wastegate bypass regulator valve pressure unit, Refer to Fuel Delivery and Air Induction.
- Check charge pressure regulating valve shaft mounting in Turbocharger for ease of movement.
If corroded together;
- Replace turbocharger.
If the charge pressure is not attained:
- Replace turbocharger assembly.
Engine Code ATW
- Press -C- button.
- Press -0-, -7- and -7- buttons to select "Display group number 77" and confirm entry with -Q button.
Indicated on Display
- Check actual charge pressure value at Wide Open Throttle in display group 4.
On a rolling test stand
Test in 3rd gear (manual transmission), 2nd gear (automatic transmission).
During test drive
Vehicles with manual transmission
- Accelerate vehicle at Wide Open Throttle in 2nd gear.
Vehicles with automatic transmission
- Manually select 4th gear range and begin accelerating from low speed at Wide Open Throttle (avoid kickdown; transmission must not shift into a lower gear).
- Press memory button "M" on turbocharger tester and read display.
^ Specification: (Relative pressure) 1.350 to 1.650 bar
- Compare actual charge pressure value with value shown in display field 3.
^ Difference: max. 100 mbar
Note: Repeat the test if the full charge pressure was not attained or if the difference between the actual value and the displayed value is exceeded.
If the charge pressure is exceeded:
- Check Charge Air Pressure sensor -G31-.
- 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 wastegate bypass regulator valve is securely mounted on turbocharger.
- Check wastegate bypass regulator valve pressure unit
- Check charge pressure regulating valve shaft mounting in turbocharger for ease of movement.
If corroded together:
- Replace turbocharger.
If the charge pressure is not attained:
- Replace turbocharger.