With Manufacturer's Scan Tool

EVAP system, checking for leaks

Special tools equipment, testers





^ V.A.G 1551 Scan Tool (or vehicle system tester V.A.G 1552) with cable VAG 1551/3

Note: All functions which could previously be performed with VAG 1551/1552 can also be performed with the new tester VAS 5051.





Test conditions
^ Fuses must be OK.
^ Battery voltage must be at least 11.5 V.
^ All electrical consumers, e.g. lights and rear window defroster must be switched off.
^ If the vehicle is equipped with air conditioning, this must be switched off.
^ Selector lever must be in position "P" or "N" on models with an automatic transmission.
^ Fuel pump relay -J17- must be OK, checking:
Refer to Electrical Wiring Diagrams, Troubleshooting & Component Locations
^ No DTC's may be stored in DTC memory:
Refer to Powertrain Management

Checking activation
- Check activation of LOP -V144- via output Diagnostic Test Mode (DTM):
Refer to Powertrain Management
If activation is OK:
- Perform functional check.

Functional check
Test conditions
^ Throttle valve angle less than 4% =display group 3, display zone 3.
^ Coolant temperature must be 85...110°C Display group 4, display zone 3.
^ Intake air temperature less than 80C°, Display group 4, display zone 4.

Test sequence
- Connect V.A.G 1551 Scan Tool (or V.A.G 1552). Start engine and select "Address word" 01 of engine control module.
Refer to Powertrain Management





Indicated on display
- Press keys O and 4 for function "Initiate basic setting" and confirm entry with Q key.





Indicated on display
- Press keys 0, 7 and 1 for"Display group number 71" and confirm entry with Q key.

Note: The engine must not be loaded during this diagnosis, if this occurs the diagnosis will be interrupted and will not start again until the engine is revved-up.





Indicated on display (14 = display zones)
If "Read op." appears in display zone 1:
- Open fuel tank filler cap briefly to release pressure in fuel tank. This will close reed contact.
If the diagnosis is initiated by the engine control module the display in display zone 4 jumps from "Test OFF" to "Test ON".

Note: If the display in display zone 4 jumps from "Test ON" to "Test OFF" during the diagnosis, repeat the diagnosis. When repeating the diagnosis test, the diagnosis can take up to 60 seconds before the display in display zone 4 jumps from "Test OFF" to "Test ON".

- Leave engine running at idling speed until display zone 4 displays specification "Syst. OK.".
If "Sys. OK." appears in display zone 4:
- Press ( arrow) key.
- Press keys 0 and 6 for function "End output" and confirm entry with Q key.
- Switch ignition off.
If "Sm leak or La leak" appears in display zone 2 and "Sys. n.OK." appears in display zone 4:
- Press (arrow) key.
- Check DTC memory:
Refer to Powertrain Management
- Read readiness code:
- Generate readiness code again if DTC memory has been erased or engine control module separated from permanent positive supply:
Refer to Powertrain Management
If no DTC is stored in DTC memory:
- Press keys O and 6 for function "End output" and confirm entry with Q key.
- Switch ignition off.
- Check that fuel tank cap is completely closed or if seal is leaking, replace as necessary.
- Repeat functional check.
If fault is still present:
- Check that fuel delivery unit union nut is tight or if seal is leaking replace as necessary.
- Repeat functional check.
If fault is still present:
- Remove rear right wheel housing liner
- Check to see if pressure hose between LDP and EVAP canister is leaking and replace if necessary.
- Check lines and line connections between EVAP canister and fuel tank flap unit or tank breather valve for leaks
- Repeat functional check.
If fault is still present:
- Remove EVAP canister and check for cracks and leaks, replace if necessary.