Audi Workshop Service and Repair Manuals

Testing for leaks

When there is no electrical signal the solenoid valve remains closed.

• ‒ Disconnect hose from the solenoid valve for the activated carbon filter (N80).
• ‒ Start final control diagnosis and select solenoid valve for activated carbon filter (N80)
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• ‒ While final control diagnosis is running, blow into solenoid valve to check whether it opens and closes properly. If necessary, fit a new solenoid valve.

Electrical test of -N80 (ACF valve)

• ‒ Unplug connector on ACF valve.
• ‒ Measure resistance between contacts on valve using hand held multimeter V.A.G 1526.

Specification: 22...30 ω.

• ‒ If the value is not as specified, fit a new ACF valve.

Testing power supply to ACF valve

Note:

The ACF valve receives its power supply via the fuel pump relay.

Test conditions

• ● Fuse for ACF valve OK.

• ‒ Unplug connector on ACF valve.
• ‒ → Connect diode test lamp V.A.G 1527 between engine earth and contact 1 on the connector.
• ‒ Operate starter.

Specification: The diode test lamp should light up.

• ‒ If diode test lamp does not light up, test for open circuit between contact 1 and fuse. Rectify open circuit if necessary.

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

• ‒ If wiring is OK, test fuel pump relay .

Testing ACF valve activation

• ‒ → Connect diode test lamp V.A.G 1527 between contact 2 (earth connection via engine control unit) and contact 1 (positive, from fuel pump relay) on the connector.
• ‒ Start final control diagnosis and select solenoid valve for activated charcoal filter (N80)
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Specification: diode test lamp should start flashing.

If the diode test lamp does not flash or lights up continuously:

• ‒ Switch off ignition.
• ‒ Connect test box V.A.G 1598/22 to wiring harness for engine control unit
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• ‒ → If the diode test lamp lights up continuously, test for short circuit to earth in wiring between contact 2 on ACF valve connector and socket 15 on 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 ACF valve connector and socket 15 on test box.
• ‒ If necessary, rectify short circuit to earth or open circuit.
• ‒ If no short circuit or open circuit is found, fit a new engine control unit
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