Audi Workshop Service and Repair Manuals

Testing for leaks

• ● When there is no electrical signal, the long connection is closed.
• ● The two short connections are connected to each other.
• ● When actuated, the link between the long connection and the two short connections is opened.

• ‒ Removing boost pressure control solenoid valve (fitting location - Item 8)
• ‒ Connect the removed valve to the wiring harness.
• ‒ Start final control diagnosis and actuate boost pressure control solenoid valve -N75 .
• ‒ Blow into the long connection during the final control diagnosis to check whether the valve opens and closes properly, if necessary replace the solenoid valve.

Electrical test of -N75

• ‒ Disconnect the plug from boost pressure control solenoid valve-N75.
• ‒ → Measure resistance between the valve contacts using hand-held multimeter V.A.G 1526.
  Specified value: 25...35 ω.
• ‒ If the specified value is not obtained, renew valve -N75.

Testing power supply of -N75

Note:

The boost pressure control solenoid valve receives its power supply via the fuel pump relay.

Test requirements:

Fuse -S29 OK

• ‒ Disconnect the plug from boost pressure control solenoid valve -N75.
• ‒ → Connect diode test lamp V.A.G 1527 between engine ground and contact 1 on the connector.

• ‒ Operate starter.

Specified value: The diode test lamp should light up.

• ‒ If the diode test lamp does not light up, test for continuity in the wiring between contact 1 and fuse -S29 according to the current flow diagram - if necessary repair open circuit.
• ‒ If wiring is OK, test fuel pump relay .

Testing actuation of boost pressure control solenoid valve -N75

• ‒ → Connect diode test lamp V.A.G 1527 between contacts 1 (positive) and 2 on the connector.
• ‒ Start final control diagnosis and actuate boost pressure control solenoid valve -N75 .

• Specified value: Diode test lamp should flash.

• ‒ If the diode test lamp does not flash or it lights up permanently, connect test box V.A.G 1598/19 to wiring harness for Motronic control unit.

• ‒ → Check wiring between contact 2 of the connector ...

• ‒ → ... and contact D3 on the Motronic control unit for continuity or short to positive and repair as necessary.
• ‒ If no wiring fault is present, replace the Motronic control unit -J220.