Audi Workshop Service and Repair Manuals

Checking charge pressure control solenoid valve -N75- Special tools and workshop equipment required

t  Hand-held multimeter -V.A.G 1526D-

t  Voltage tester -V.A.G 1527B-

t  Auxiliary measuring set -V.A.G 1594C-

t  Adapter -V.A.G 1598/19- (engine codes AEB, AJL up to 06.96) t  Adapter -V.A.G 1598/22- (engine codes AEB, AJL from 07.96 onwards) t  Adapter cable, 121-pin -V.A.G 1598/31- (engine codes ANB, APU, ARK, ATW) t  Vehicle diagnostic, testing and information system -VAS 5051B- Procedure   Note The charge pressure control solenoid valve -N75- and its wiring are monitored by the engine control unit. 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 diagnostic function “Interrogate fault memory” and press → key to continue. If the display shows a fault relating to charge pressure control solenoid valve -N75-: –  Press ← key to terminate function “Interrogate fault memory”. –  Select “End output”. –  Switch off ignition.

Checking operation –  Detach hoses from solenoid valve for charge pressure control -N75-; leave connector attached. –  Connect test hose to hose connection on solenoid valve for charge pressure control -N75- marked with an -arrow-.

–  Switch on ignition and select vehicle system “01 - Engine electronics” again. Display on -VAS 5051B-: –  From menu -1-, select diagnostic function “Final control diagnosis” and press → key to continue.

–  Press the → key repeatedly until the following display appears: Display on -VAS 5051B-: 4 -  Charge pressure control solenoid valve -N75- A -  Actuator is running; continued switching is allowed l  The valve will be activated intermittently for approx. 1 minute (and should click audibly). l  The valve should open and close (check by blowing into the test hose). –  Press ← key to terminate diagnostic function “Final control diagnosis”. –  Select function “End output” and switch off ignition. If valve clicks but does not open or close correctly: –  Renew charge pressure control solenoid valve -N75-. If the valve is not activated (does not click):

Checking internal resistance –  Unplug electrical connector at charge pressure control solenoid valve -N75-. –  Connect hand-held multimeter -V.A.G 1526D- to valve (resistance measurement range). l  Specification: 25 ... 35 Ω. –  If reading does not match specification, renew solenoid valve for charge pressure control -N75-. If the specification is attained: Checking voltage supply l  Fuse for charge pressure control solenoid valve -N75- OK → Current flow diagrams, Electrical fault finding and Fitting locations. l  Fuel pump relay -J17- OK; checking → Rep. Gr.24   Note Charge pressure control solenoid valve -N75- is supplied with power via fuel pump relay -J17-.

–  Connect voltage tester -V.A.G 1527B- between contact -1- of connector for charge pressure control solenoid valve -N75- and earth “–”. –  Briefly operate starter. l  The LED should light up. –  If LED does not light up, check for open circuit in wiring from contact -1- of connector for solenoid valve for charge pressure control -N75- via fuse to fuel pump relay -J17- → Current flow diagrams, Electrical fault finding and Fitting locations. –  Repair wiring connection if necessary. If the LED lights up:

Checking activation –  Connect voltage tester -V.A.G 1527B- between contacts -1- and -2- of connector for charge pressure control solenoid valve -N75-.

–  Switch on ignition and select vehicle system “01 - Engine electronics” again. –  Repeat diagnostic function “Final control diagnosis”. –  Press the → key repeatedly until the following display appears: Display on -VAS 5051B- (example): A -  5th control element being tested 5 -  Charge pressure control solenoid valve -N75- l  The LED should flash. If the LED does not flash or lights up continuously:

Vehicles with engine codes AEB, AJL up to 06.96: –  Connect adapter -V.A.G 1598/19- (test box) to connectors of wiring harness; do not connect engine control unit → Rep. Gr.24. –  Check for open circuit and short to positive or earth in the following wiring for charge pressure control solenoid valve -N75-.

Connector Contact	-V.A.G 1598/19- Socket
-2-	D3

Vehicles with engine codes AEB, AJL from 07.96 onwards: –  Connect adapter -V.A.G 1598/19- (test box) to connectors of wiring harness; do not connect engine control unit → Rep. Gr.24. –  Check for open circuit and short to positive or earth in the following wiring for charge pressure control solenoid valve -N75-.

Connector Contact	-V.A.G 1598/19- Socket
-2-	64

Vehicles with engine codes ANB, APU, ARK, ATW: –  Connect adapter cable, 121-pin -V.A.G 1598/31- (test box) to connectors of wiring harness; do not connect engine control unit. Connect earth clip of test box to earth → Rep. Gr.24.

–  Check for open circuit and short to positive or earth in the following wiring for charge pressure control solenoid valve -N75-.

Connector Contact	-V.A.G 1598/31- Socket
-2-	104

All vehicles (continued): –  Repair wiring connection if necessary.