EVAP System, Checking For Leaks

WARNING: This page is about a different car, the 2024 Audi A4 Quattro. However, it is still accessible from the selected car via links, so may be relevant.

The following procedure is used to diagnose EVAP System leaks.

Special tools and workshop equipment required

Smoke tester.
EVAP and Fuel Supply System Vacuum hose and line routing diagram.

Leak checking

-- Using a Smoke tester, check the Evaporative Emission (EVAP) canister system for leaks.

-- Always follow the manufacturers directions for the proper installation and operation of the smoke tester being used.

If a leak is detected:

-- Check the fuel filler cap seal for damage and for proper installation. Replace if necessary.

-- Check all hose connections of the fuel supply system and replace or repair any leaking lines.

-- Check all hose connections of the EVAP system and replace or repair any leaking lines.

-- Check that the seal under the locking flange is properly tightened on the fuel tank.

-- Secure all hose connections using appropriate fittings for the model type.

-- Replace seals and gaskets when performing repair work.

-- Repair or replace any damaged component.

If no leaks are found in the EVAP system:

-- Erase the DTC memory if a DTC was set. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .

-- Perform a road test to verify repair.

If a DTC was set and does not return:

Diagnosis complete. Generate readiness code. Refer to READINESS CODE .

If the same DTC does return and no leaks are found in the EVAP system:

-- Check for any related TSB's.

-- Perform the diagnostic test procedure for the suspected component.