Evaporative Emissions System: Testing and Inspection
EVAP System, Checking For Proper Seal
Special tools and equipment
- VAG1551 scan tool (or VAG1552 mobile scan tool) with VAG1551/3B cable
Test requirements
- All fuses must be OK.
- No DTCs in DTC memory
- Sealing cap closed or seal for sealing cap in working order
- If vehicle is equipped with an A/C system, it must be switched off.
- Coolant temperature must be at least 80 °C, See Display group 04, display field 3
- Intake Air Temperature (IAT) less than 90 °C See Display group 004, display field 4
- Throttle valve in idle position See Display group 005, display field 4.
Function test
- Connect VAG 1551 scan tool (VAG1552). Start engine and select the Engine Control Module (ECM) using address word 01. Connecting scan tool and selecting Engine Control-Module (ECM):
Indicated on display:
Rapid data transfer HELP
Select function XX
- Press buttons -0- and -4- to select "Basic Setting" function 04. Press -Q- button to confirm input.
Indicated on display:
Basic Setting HELP
Enter display group number XXX
- Press 0, 7 and 1 for the function "display group number 71", and then press Q to exit from input mode.
Indicated on display: (1 to 4 = display fields)
Basic setting 71 ->
1 2 3 4
- Check indication in display field 4.
Display Group 71:
- Diagnostic takes approx. 3 minutes.
- If specified values are obtained in all display fields, press -> button.
Indicated on display:
Rapid data transfer HELP
Select function XX
- Press buttons -0- and -6- to select "End data transfer" function 06. Press -Q- button to confirm input.
If specified values are not obtained:
- Check EVAP system for leaks.
Checking proper seal
- Connect Scan Tool (ST) VAG1551
If a small or large leak was recognized during test of the EVAP system or if a malfunction is stored in DTC memory, proceed as follows:
- Check DTC memory, repair malfunctions if necessary and then erase DTC memory.
- Then:
- Connect Scan Tool (ST) VAG1551
Indicated on display:
Rapid data transfer HELP
Select function XX
- Press buttons -0- and -4- to select "Basic Setting" function 04. Press -Q- button to confirm input.
Indicated on display:
Basic Setting HELP
Enter display group number XXX
- Press 0, 7 and 1 for the function "display group number 71", and then press Q to exit from input mode.
Indicated on display: (1 to 4 = display fields)
Basic setting 71 ->
1 2 3 4
Test of EVAP system will be initiated. Indication in display field 4 shows which function of the diagnostic is currently active.
- Check specified values in display fields 3 and 4
If the diagnostic was ended successfully, the specified values must appear as follows:
Display Group 71:
If specified values are not obtained:
- Repeat function test.
- Check DTC memory, repair malfunctions if necessary and then erase DTC memory.
If malfunction persists:
- Switch ignition off.
- Check whether filler cap for fuel tank is completely closed and whether seal is in proper order.
- Check connecting lines and hoses from EVAP canister to fuel flap unit and EVAP valve.
- Check hose connections of EVAP system in engine compartment.
If malfunction persists:
- Check hoses and hose clamps for secure seating.
- Check whether lock ring for Fuel Pump (FP) is tightened or whether seal is faulty, replace if necessary. Use 3217 ring nut spanner to re-tighten lock ring.
- Remove EVAP canister and check for tears and leaks, replace if necessary.
- Repeat function test.
If malfunction persists:
- Press -> button.
Indicated on display:
Rapid data transfer HELP
Select function XX
- Press buttons -0- and -6- to select "End data transfer" function 06. Press -Q- button to confirm input.
- Check Evaporative Emission (EVAP) canister purge solenoid valve -N115-. Testing and Inspection