Work sequence

WARNING: This page is about a different car, the 2006 Audi A4, 2005 Audi A4, 2004 Audi A4, and 2003 Audi A4. However, it is still accessible from the selected car via links, so may be relevant.

CAUTION: Always attach testers and measuring instruments to back seat and have them operated from there by a second person.

If testers and measuring instruments were to be operated from front passengers seat, person sitting there could suffer injury in the event of an accident due to triggering of front passengers airbag.

Fig 1: Connecting T-Piece And Measuring Hose Of Turbocharger Tester VAG1397A To Intake Manifold

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Connect T-piece and measuring hose of turbocharger tester VAG1397A to intake manifold (front).
Route measuring hose under rear edge of hood and into passenger compartment via right side window.

Fig 2: Identifying Turbocharger Tester V.A.G 1397 A

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Switch on turbocharger tester and set measuring range selector switch to position -I- (absolute pressure).
Connect measuring hose to connection -I-.

NOTE:

Hose connections must be completely airtight, otherwise measurements will not be correct.
Ensure that measuring hose is not pinched at hood or side window.
Pressing memory key -M- on turbocharger tester will store last measured value until memory key -M- is pressed again or tester is switched off.
The decimal point in display flashes to indicate that value is being stored.
If battery voltage of turbocharger tester drops below minimum level, an arrow will appear at top left of display.
Before performing test, drive vehicle at brisk speed for at least 3 km without stopping (i.e. along route without traffic lights, etc.).
A second mechanic is required to note readings on tester when vehicle is moving.

Reading measured value block 115 →
1 2 3 4

Read measured value block, display group 115, engine idling.
Accelerate vehicle from 2000 RPM to wide open throttle in third gear and watch rev counter.
At approx. 2500 RPM, press print key on VAS5051 or PRINT key on VAG1551 while simultaneously pressing memory key -M- on VAG1397A.

Fig 3: Identifying Turbocharger Tester V.A.G 1397 A

Courtesy of VOLKSWAGEN UNITED STATES, INC.

NOTE:

The charge air pressure should be measured using turbocharger tester VAG1397/A. Vehicle diagnostic, testing and information system VAS5051 or scan tool VAG1551 is used to check whether charge air pressure is being registered by control module.
Specification for VAG1397A : 1.500 to 1.600 bar
Specification on VAG1551 or VAS5051 in display zone 4:

Reading measured value block 115 →
1 2 3 4

1500 to 1600 mbar

If reading does not match specification, troubleshooting table.

Malfunctions in charge air pressure control

Malfunction	Possible cause of trouble
Charge air pressure below specification	Wastegate bypass regulator valve N75 faulty → Wastegate bypass regulator valve N75 , checking , checking Hoses to Wastegate bypass regulator valve N75 faulty, → Boost pressure regulation and vacuum control system, connection diagram for vehicles up to 06.03 , connection diagram or → Boost pressure regulation and vacuum control system, connection diagram for vehicles as of 07.03 , connection diagram Charge pressure control valve in turbocharger sticking in open position Leak between turbocharger and intake manifold → Effects of leakage at intake and exhaust end , effects Mechanical air recirculation valve faulty → Mechanical air recirculation valve, checking , checking Recirculating valve for turbocharger N249 faulty → Recirculating valve for turbocharger N249 , checking , checking Turbocharger faulty → Turbocharger, removing and installing , replacing
Charge air pressure above specification * See note	Vacuum unit for charge air pressure control valve faulty → Turbocharger, removing and installing , replacing Hoses to vacuum unit for charge air pressure control (via N75 leaking → Boost pressure regulation and vacuum control system, connection diagram for vehicles up to 06.03 , connection diagram or → Boost pressure regulation and vacuum control system, connection diagram for vehicles as of 07.03 , connection diagram Charge air pressure control valve in turbocharger sticking in closed position → Turbocharger, removing and installing , replacing

Malfunction

Possible cause of trouble

Charge air pressure below specification

Wastegate bypass regulator valve N75 faulty → Wastegate bypass regulator valve N75 , checking , checking
Hoses to Wastegate bypass regulator valve N75 faulty, → Boost pressure regulation and vacuum control system, connection diagram for vehicles up to 06.03 , connection diagram or → Boost pressure regulation and vacuum control system, connection diagram for vehicles as of 07.03 , connection diagram

Charge pressure control valve in turbocharger sticking in open position
Leak between turbocharger and intake manifold → Effects of leakage at intake and exhaust end , effects

Mechanical air recirculation valve faulty → Mechanical air recirculation valve, checking , checking
Recirculating valve for turbocharger N249 faulty → Recirculating valve for turbocharger N249 , checking , checking

Turbocharger faulty → Turbocharger, removing and installing , replacing

Charge air pressure above specification * See note

Vacuum unit for charge air pressure control valve faulty → Turbocharger, removing and installing , replacing
Hoses to vacuum unit for charge air pressure control (via N75 leaking → Boost pressure regulation and vacuum control system, connection diagram for vehicles up to 06.03 , connection diagram or → Boost pressure regulation and vacuum control system, connection diagram for vehicles as of 07.03 , connection diagram

Charge air pressure control valve in turbocharger sticking in closed position → Turbocharger, removing and installing , replacing

*If charge air pressure is too high, fuel supply will be interrupted in order to protect engine. This results in misfiring at high engine speeds.