Audi Workshop Service and Repair Manuals

Checking operation

• ‒ Pull the hoses off the -N75 solenoid valve for boost pressure control
  => Fitting locations -Overview - Page 24-5.
• ‒ Connect auxiliary hose.
• ‒ Start the final control diagnosis and actuate the -N75 solenoid valve for boost pressure control .

• The valve should click...
• ...and should open and close (check by blowing into the auxiliary hose).

If the valve does not click:

• ‒ Check the solenoid valve for boost pressure control electrically .

• When there is no electrical signal, the long connection is closed.

If the solenoid valve clicks, but does not open and close properly:

• ‒ Replace the solenoid valve for boost pressure control (N75).

Electrical check on solenoid valve for boost pressure control (N75).

• ‒ Unplug the connector from the valve
  => Fitting locations - Overview - Page 24-5.
• ‒ → Connect the V.A.G 1526 hand held multimeter for resistance measurement to the valve.

• Specified value: 25...35 ω.

If the specified value is not achieved:

• ‒ Replace the solenoid valve for boost pressure control (N75).

If the specified value is achieved:

• ‒ Check the power supply from the solenoid valve for boost pressure control => Page 24-38.

Check the power supply to the solenoid valve for boost pressure control (N75).

• ‒ → Connect the V.A.G 1526 hand held multimeter for voltage measurement to contact 1 of the connector and the earth.
• ‒ Operate the starter briefly (the engine may start briefly).

• Specified value: approx. battery voltage.

If the specified value is not achieved:

• ‒ Check the wiring from contact 1 on the connector via the fuse to the fuel pump relay for an open circuit or short circuit.

=> Current Flow Diagrams, Electrical Fault Finding and Fitting Locations binder

If the specified value is achieved:

• ‒ Check the actuation for the solenoid valve for boost pressure control => Page 24-39.

Checking the actuation of the solenoid valve for the boost pressure control (N75)

• ‒ Unplug the connector from the solenoid valve (N75) and connect the V.A.G 1527 diode test lamp between connector contacts 1 and 2.
• ‒ Start the final control diagnosis and actuate the N75 solenoid valve for boost pressure control .

The diode test lamp should start flashing.

• ‒ If diode test lamp does not flash or if the lamp is lit continuously. Check the wiring.
• ‒ Connect the V.A.G 1598/22 test box to the wiring harness for the engine control unit
  .

→ The following wiring should be checked for a short to positive or negative and an open circuit:

• ‒ If necessary, rectify open circuit or short circuit.