EVAP System, Leak Testing Using VAS5051 or VAG1551
Observe safety precautions
Observe rules of cleanliness
CAUTION!
- Always refer to the latest parts catalog to ensure that you use original equipment fuel hose clamps.
- O-rings and gaskets should always be replaced during repair work.
Test requirements
- Parking brake applied
- Gear selector lever in P or N
- No DTCs in DTC memory
- Electrical consumers switched off (radiator fan must NOT run during test)
- A/C switched off
- Intake Air Temperature (IAT) less than 90 °C, see display group 004, display field 4.
- Coolant Temperature less than 95 °C, see display group 004, display field 3.
- Throttle valve angle less than 10°, see to display group 003, display field 3.
Procedure
- Connect VAS5051 with diagnostic cable VAS5051/1 or VAG1551 scan tool with diagnostic cable VAG1551/3A.
NOTE: The following description only explains implementation of On Board Diagnostic (OBD) using VAG1551 scan tool. When using VAS5051, observe the tester's instructions for use.
- Start engine and run at idle.
- Press button 1 to select "Rapid data transfer" operating mode 1.
Indicated on display
Rapid data transfer HELP
Insert address word XX
- Press buttons -0- and -1- to select "Engine electronics" and press -Q- button to confirm input.
- Press -button.
Indicated on display
Rapid data transfer HELP
Select function XX
- Press buttons -0- and -8- to select "Read Measuring Value Block" and press -Q- button to confirm input.
Indicated on display
Read Measuring Value Block
Input display group number XXX
- Press buttons -0-, -7- and -1- to select display group number 071 and press -Q- button to confirm input.
Indicated on display
Read Measuring Value Block 71 ->
Reed cl Abort Test OFF
NOTE:
- If "Reed cl" (closed) is displayed, continue test.
- "Abort" does not always appear on display.
- If display indicates "Reed open", briefly open and close fuel filler cap to release pressure from fuel tank. This will close the reed contact. Continue test as follows:
- Press button -4- to select "Basic setting" operating mode 4.
If indicated on display
System in Basic Setting 71 ->
Reed closed Test ON
The Evaporative Emission (EVAP) Canister Purge Regulator Valve -N80 will be opened briefly to release pressure (purge) in system.
Then the Leak Detection Pump (LDP) -V144 will be activated, the process will last approx. 60 seconds.
Indicated on display
System in Basic Setting 71 ->
Reed open Syst.Test Test ON
System is performing a system test. Then the LDP -V144 will start up. It will shut off when the pump time has run out. The process will last about 60 seconds.
Indicated on display
System in Basic Setting 71 ->
Reed open Check Test ON
Measuring phase begins. LDP is switched off and the Engine Control Module (ECM) checks whether the reed contacts closes within 10 seconds:
If reed contact does not close within 10 seconds:
Indicated on display
System in Basic Setting 71 ->
Reed open Check. END Syst.OK
System is sealed, test is terminated
- Press -> button.
- Press buttons -0- and -6- to select "End Output" and press -Q- button to confirm input.
If reed contact does close within 10 seconds:
The Leak Detection Pump (LDP) -V144 will pump four additional strokes for an additional measurement. The Engine Control Module (ECM) compares the time required for these four strokes and time closure of the reed contact.
Indicated on display. System has a small leak (smaller than 1 mm in diameter).
System in Basic Setting 71 ->
Reed cl Sm. Leak.END Syst.n.OK
Indicated on display. System recognized a large leak.
System in Basic Setting 71 ->
Reed cl Lg. Leak END Syst.n.OK
- Press -> button.
- If the system has detected a small or large leak, check fuel supply system and tank ventilation system for leaks and repair as necessary.
- After repairs are completed, repeat leak test.
Checking fuel supply and tank ventilation system for leaks
NOTE: The following describes areas in the fuel supply and ventilation system that should be checked for possible leaks. After making necessary repairs, perform leak test again to ensure that all leaks were successfully repaired.
- Switch ignition off.
- Check if fuel filler cap was completely closed for test.
- Check if seal of fuel filler cap is damaged, replace if necessary.
- Remove covers for fuel level senders and fuel delivery module on left and right side under carpet in trunk.
- Check whether seals under connection flanges are OK and ring nuts are properly tightened. Also check if fuel line connections are tight.
NOTE: Observe installation notes for connector flanges, refer to "Fuel Delivery Module, Removing and Installing" Service and Repair
- Check whether O-rings for fuel level sender (item 4) and securing bolt (item 14), refer to "Fuel Delivery Module and Fuel Level Senders, Removing and Installing" Service and Repair
- Visually check all lines and hose connections of tank ventilation system and replace leaky lines, e.g.:
- Line from fuel tank to fuel expansion tank.
- Line EVAP canister to EVAP canister purge regulator valve (in engine compartment).
- Lines from EVAP canister to Leak Detection Pump (LDP) (under left rear wheelhousing liner).
- Line from fuel expansion tank to EVAP canister (under cover for EVAP canister).
- Lines from EVAP system (tank ventilation system).
- Fuel lines to engine.
NOTE: Leaks at lines and components of fuel supply system can sometime be located using a nonflammable, environmentally sound leak detection spray. For this, initiate leak test several times in sequence to build pressure in the system. Leaks can be detected via bubbles forming at the leak.
- Visually check components of fuel supply system and EVAP system.
- Fuel tank
- EVAP canister
- Leak Detection Pump (LDP) -V144
- Evaporative Emission (EVAP) canister purge regulator valve -N80
NOTE:
- Because of the shape or function of these components it is not always possible to detect leaks by applying spray. It may be necessary to clamp off the relevant component using 3094 hose clamp and initiate the leak detection diagnostic. If the leak is no longer detected, the component that was clamped off if faulty. If the clamp is directly on the diagnostic pump and a leak is still detected, then the diagnostic pump itself is leaking.
- Checking Evaporative Emission (EVAP) Canister Purge Regulator Valve -N80