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 1526 C- or -V.A.G 1526 A-

t	Voltage tester -V.A.G 1527 B-

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

t	Adapter cable -V.A.G 1598/31- (test box)

t	Vehicle diagnostic, testing and information system -VAS 5051- with diagnosis lead -VAS 5051/1-

Procedure   Note The charge pressure control solenoid valve -N75- and its wiring are monitored by the engine control unit. –  Connect up vehicle diagnostic, testing and information system -VAS 5051- with diagnosis lead -VAS 5051/1-, press vehicle self-diagnosis button and select vehicle system “01 - Engine electronics”. When doing this, the engine must be running at idling speed.

Display on -VAS 5051-: –  From list -1-, select diagnosis function “02 - Interrogate fault memory”. If the display shows a fault relating to charge pressure control valve -N75-: –  Terminate function “02 - Interrogate fault memory” by touching ← key. –  Press function “06 - End output” and switch off ignition.

–  Take off engine cover panel -arrows-.

–  Disconnect hoses -5- and -6- (plus an additional hose not shown in illustration) from charge pressure control solenoid valve -N75-; leave electrical connector -4- attached.   Note Ignore other -items-.

–  Connect test hose to the long hose connection -arrow- on charge pressure control solenoid valve -N75-.

–  Switch on ignition and select vehicle system “01 - Engine electronics”. Display on -VAS 5051-: –  From the menu -1- select the diagnostic function “03 - Final control diagnosis”.

–  Press the → key repeatedly until the following display appears: Display on -VAS 5051- (example): A -  2nd control element being tested 2 -  Charge pressure control solenoid valve -N75- l  The valve should click and open and close (check by blowing into the test hose). –  Press the ← key to exit from function “03 - Final control diagnosis”. –  Press function “06 - End output” and switch off ignition. If valve clicks but does not open or close correctly: –  Renew charge pressure control solenoid valve -N75-. If valve does not click:

Checking internal resistance –  Disconnect electrical connector -4- at charge pressure control solenoid valve -N75-.   Note Ignore other -items-.

–  Connect hand-held multimeter -V.A.G 1526 C- to measure resistance between contacts of charge pressure control solenoid valve -N75-. l  Specification: 25 ... 35 Ω. If the specification is not attained: –  Renew charge pressure control solenoid valve -N75-. If specification is obtained: 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 → Current flow diagrams, Electrical fault finding and Fitting locations.   Note Charge pressure control solenoid valve -N75- is supplied with power via fuel pump relay -J17-.

–  Connect voltage tester -V.A.G 1527 B- between contact -1- of connector for charge pressure control solenoid valve -N75- and earth “–”. –  Operate the starter briefly. l  The LED should light up. If LED does not light up: –  Check for open circuit in wiring from contact -1- of connector for charge pressure solenoid valve -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 1527 B- between contact -1- and -2- of connector for charge pressure control solenoid valve -N75-. –  Switch on ignition and select vehicle system “01 - Engine electronics”. –  Repeat function “03 - Final control diagnosis”.

–  Press the → key repeatedly until the following display appears: Display on -VAS 5051- (example): A -  2nd control element being tested 2 -  Charge pressure control solenoid valve -N75- l  The LED should flash. –  Press the ← key to exit from function “03 - Final control diagnosis”. –  Press function “06 - End output”. –  Switch off ignition and unplug diagnostic connector.

If the LED does not flash or lights up continuously: –  Connect adapter cable -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 -arrow- → Rep. Gr.24.   Caution To prevent damage to electronic components, select appropriate measuring range before connecting measuring leads and observe test requirements. –  Check for open circuit and short to positive or earth in the following wiring:

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

–  Repair wiring connection if necessary. Assembling Installation is carried out in the reverse order; note the following:   Note Secure all hose connections with the correct type of hose clips (same as original equipment) → Parts catalogue.