Evaporative Emission (EVAP) canister system, checking for proper seal

WARNING: This page is about a different car, the 2006 Audi A4, 2005 Audi A4, 2004 Audi A4, 2003 Audi A4, and 2002 Audi A4. However, it is still accessible from the selected car via links, so may be relevant.

NOTE:

Secure all hose connections using hose clamps appropriate for the model type .
Replace seals and gaskets when performing repair work.

Test sequence

Connect the scan tool.
Start the engine and let run at idle for at least 15 minutes.
Select "Diagnostic mode 8: Tank leak test".
Select the "OBDMID 01: Tank leak test" and check the specified value at idle.

Specified value: test OK

NOTE:

If the accelerator pedal is depressed during the test, the test will be aborted.
To repeat the tank leak-tightness test, switch the ignition off, start the engine again, and let it run at idle.

If the specified value is obtained:

End diagnosis and switch the ignition off.

If the specified value is not obtained:

Checking fuel supply and tank ventilation systems for leaks

Ensure the fuel filler cap is properly installed on the fuel tank.
Check the fuel filler cap seal for damage. Replace if necessary.
Remove the rear seat bench →
- 72 - SEAT - FRAMES
- 72 - SEAT - FRAMES for BODY INTERIOR - CABRIOLET
.

Fig 1: Releasing Retaining Tabs

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Release the retaining tabs - arrows -.
Release the retaining tabs - 1 - and - 3 -.

Fig 2: Folding Cover Toward Front

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Lift the cover - 2 - toward the front - arrow -.

Fig 3: Unbolting Cover

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Unbolt the cover - arrows -.

Fig 4: Removing Cover Bolts For Locking Flange

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Remove the bolts - arrows - and cover.
Check the seals under the locking flanges are OK and the union nuts are properly tightened on the fuel tank. Also check the fuel line connections.
Visually check all hose connections of the fuel supply system and replace any leaking lines, e.g:

Check the line from the EVAP canister to the Evaporative Emission (EVAP) Canister Purge Regulator Valve N80.
Check the lines from the EVAP canister to the Leak Detection Pump (LDP) V144.
Check the line from the fuel tank to the EVAP canister (below cover for EVAP canister).
Check the lines for the tank ventilation (beneath right rear wheel housing liner).

Check the fuel lines to the engine.

NOTE:

Leaks at the lines and components of the fuel tank ventilation system can sometimes be located using a non-flammable, environmentally compliant leak detection spray. Initiate the leak diagnosis several times in sequence to build up pressure in the system. At leaking areas, bubbles will form.

Repeat the function test.

If a leak is detected:

Perform a visual inspection on the fuel system components and tank ventilation system.

Fuel tank.
EVAP canister.
Leak Detection Pump (LDP) V144.
Evaporative Emission (EVAP) Canister Purge Regulator Valve N80.

NOTE:

Due to the form or function of the components, leaking areas may not always be localized by spraying on the leak detection spray. It may be necessary to clamp off the relevant component using Hose Clamps Up To 25mm Dia. and initiate the tank leak detection diagnostic. If the leak is no longer indicated, the component that was clamped off is faulty. If clamped off directly at the leak detection pump and a leak is still indicated, the leak detection pump itself is leaking.

Final procedures

After the repair work, the following work steps must be performed in the following sequence:

Check the DTC memory.
If necessary, erase the DTC memory. Refer to Diagnostic Mode 04: Reset/delete diagnostic data .
If the DTC memory was erased, generate readiness code. Refer to Readiness Code .

End of diagnosis.