Audi Workshop Service and Repair Manuals

Note:

The electrical solenoid valve for intake air change-over valve -N335 actuates a mechanical valve through vacuum, which is housed in the air cleaner housing.

The electrical valve can be tested via the final control diagnosis. On actuation of the valve during final control diagnosis, the electric valve has to click and a changeover of the mechanical valve must be clearly audible.

Before dismantling anything, carry out final control diagnosis and note whether both valves (electric as well as mechanical in air cleaner housing) are audible on actuation of electric valve. The mechanical valve can be heard until vacuum in vacuum reserve is used up (approx. 5 change-overs)

Briefly start the engine, to be able to carry out another final control diagnosis after opening of possible hoses (i.e. to subsequently test actuation of electric valve from engine control unit).

• ‒ → Undo screw fastenings -arrows- and remove engine covers -A...C-.

• ‒ → Remove air duct -arrows-.

The intake air change-over valve -N335 and secondary air inlet valve -N112 are both secured to a common bracket below exhaust gas temperature senders. The bracket in turn is secured to the suction pipe with the fastening screws of the exhaust gas temperature senders. To carry out measurements, the bracket together with exhaust gas temperature sender must be detached.

•     1 -    → Combination valve for secondary air inlet (bank 1)
•     2 -    Exhaust gas temperature senders -G235 and -G236
•     3 -    Intake air change-over valve -N335
•     4 -    Secondary air inlet valve -N112
•     5 -    Secondary air pump motor -V101
•     6 -    Secondary air inlet combination valve (bank 2)

Electrical testing of intake air change-over valve -N335

Fitting location .

• ‒ Unplug connector from intake air change-over valve -N335.
• ‒ → Measure resistance between the valve contacts using V.A.G 1526.

• Specified value: 25...35 Ohms

• ‒ If specified value is not attained, replace intake air change-over valve -N335.

Testing power supply to intake air change-over valve -N335

• ‒ → Unplug connector from intake air change-over valve -N335.

• ‒ → Connect diode test lamp V.A.G 1527 between engine earth and contact 1 on connector using cables from adapter set V.A.G 1594.
• ‒ Operate the starter briefly.

The diode test lamp should light up.

If the diode test lamp does not light up, carry out the following tests:

• ‒ Test fuse for -N335
• ‒ Test for open circuit in wiring between fuse and contact 1 on connector for intake air change-over valve using current flow diagram.

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

Specified value: max. 1 ω.

• ‒ Check the fuel pump relay and actuation .

Testing actuation of intake air change-over valve

• ‒ → Connect diode test lamp V.A.G 1527 between contacts 1 and 2 on connector for intake air change-over valve using cables from adapter set V.A.G 1594.
• ‒ Start final control diagnosis . Diode test lamp must flash on actuation of intake air change-over valve.

• ‒ → If the diode test lamp does not flash or lights up continuously, connect test box V.A.G 1598/31 to wiring harness for engine control unit, do not connect engine control unit.
  .
• ‒ If the diode test lamp lights up continuously, test for short to earth in wiring between contact 2 on connector for intake air change-over valve and socket 105 on V.A.G 1598/31 test box.

• ‒ If the diode test lamp does not flash, test for open circuits and short circuits to positive in the wiring between contact 2 on intake air change-over valve connector and socket 105 on test box.

Specified value: max. 1 ω.

• ‒ Rectify the short-circuit or open-circuit as appropriate.
• ‒ If no open circuits or short circuits are found, fit a new engine control unit .