Audi Workshop Service and Repair Manuals

Checking turbocharger and charge pressure regulating valve - engine codes ANB, APU, ARK, ATW Special tools and workshop equipment required

t  Turbocharger tester -V.A.G 1397A- t  Vehicle diagnostic, testing and information system -VAS 5051B-

Procedure l  All hoses and pipes securely fitted and and free of leaks. l  Fault memory interrogated, final control diagnosis performed → Vehicle diagnosis, testing and information system VAS 5051. –  Connect T-piece with hose of turbocharger tester -V.A.G 1397A- to intake manifold (front). –  Route test hose under rear edge of bonnet and through right window into passenger compartment.

–  Switch on turbocharger tester and set measuring range selector switch to position -I- (absolute pressure). –  Fit test hose to connection -I-.   Note t  Ensure absolute leakproof connection of hoses to avoid measurement errors. t  Take care not to trap test hose at bonnet and side window. t  Pressing memory button -M- on turbocharger tester causes last measured value to be stored until memory button -M- is pressed again or tester is switched off. t  The decimal point in the display flashes to indicate that the value is being stored. t  If the battery voltage of the turbocharger tester drops below the minimum level, an arrow will appear at the top left of the display. t  Before performing the test, drive vehicle moderately fast for at least 3 km (without stopping at traffic lights etc.).   WARNING Accidents can be caused if the driver is distracted by test equipment while road-testing, or if test equipment is not properly secured. Observe safety precautions → Chapter. l  Charge pressure is measured under full load while driving or on a roller dynamometer. l  Test duration per measurement: max. 10 seconds l  Vehicle diagnostic, testing and information system -VAS 5051B- connected. l  Engine running. l  Vehicle self-diagnosis and vehicle system “01 - Engine electronics” selected.

Display on -VAS 5051B-: –  From menu -1-, select diagnosis function “Measured values” and press → key to continue.

Display on -VAS 5051B-: –  Press keys 115 on keypad -1- to select “Display group 115” and confirm entry by pressing Q key. –  Accelerate vehicle in 3rd gear (or position 2) from 2000 rpm at full throttle while a second mechanic observes the rev counter. –  Have the second mechanic press PRINT key on -VAS 5051B- and memory key -M- on -V.A.G 1397A- simultaneously at approx. 2500 rpm.   Note The charge pressure should be measured using turbocharger tester -V.A.G 1397A-. Vehicle diagnostic, testing and information system -VAS 5051B- is used to check whether the charge pressure is being registered by the control unit.

Display on -V.A.G 1397 A-: l  Specification: 1.500 ... 1.600 bar.

Display on -VAS 5051B-: –  Check display in display zone -4-. l  Specification: 1500 … 1600 mbar.

If the specification is not attained:

Fault	Possible causes
Charge pressure below specification	t  Hose connections to charge pressure control solenoid valve -N75- defective. Connection diagram → Chapter t  Charge pressure control solenoid valve -N75- defective. Checking → Chapter t  Charge pressure regulating valve in turbocharger stuck in open position. Renew turbocharger → Chapter t  Leak between turbocharger and intake manifold. Effects → Chapter t  Mechanical air recirculation valve defective. Checking → Chapter t  Turbocharger air recirculation valve -N249- defective. Checking → Chapter t  Turbocharger defective. Renewing → Chapter
Charge pressure above specification 1)	t  Vacuum unit for charge pressure regulating valve defective. Renew turbocharger → Chapter t  Air leaks in hoses or connections to vacuum unit for charge pressure control (via solenoid valve for charge pressure control -N75-). Connection diagram → Chapter t  Charge pressure regulating valve in turbocharger sticking in closed position. Renew turbocharger → Chapter
l  1) If the charge pressure is too high the fuel supply will be shut off in order to protect the engine. Misfiring will then occur at high engine speeds.

If specification is obtained: –  Select “End output”. –  Switch off ignition and unplug diagnostic connector.