P0441

P0441
Fuel Tank Ventilation Malfunction

Function
The fuel vapors from the fuel tank must not escape into the open air. For this reason, the ventilation line of the fuel tank is routed to an evaporative emission filter that retains the fuel vapors. When driving, air is drawn in through the evaporative emission filter which picks up the accumulated fuel vapors and feeds them to the combustion process.

Diagnosis conditions
- Engine at idle.
- Vehicle speed = 0 km/h.
- Oxygen sensing active.
- Time elapsed after engine start-up > 1000 seconds
- No secondary air injection.
- Engine load < 1.4 ms.
- Air mass < 50 kg/h.
- Engine temperature at time of engine start-up >/= - 10.5°C.
- Engine temperature >/= 110°C.
- The vehicle must not be at an altitude of above 2448 m.
- No faults: Throttle position sensor, idle air control, vehicle speed, EVAP canister purge valve end stage, idle air control valve, mass air flow,sensor, load signal, voltage supply and engine temperature.

NOTE:
- Fuel tank ventilation diagnosis is aborted if the nominal idle speed changes by more than 60 1/min, the pilot air by more than 0.8 kg/h or the nominal air mass by more than 1.4 kg/h.
- Fuel tank ventilation diagnosis can be initiated in the menu Short test" with the system tester. As a result, the 1000 seconds after engine start-up are not active.





System overview
1. EVAP canister purge valve
2. Evap. emission filter
3. Purge air
4. Fuel tank
5. Intake manifold
6. Engine





Wiring diagram.





Diagnostic procedure
Check installation position of EVAP canister purge valve.
Flow through the EVAP canister purge valve is possible in one direction only. The flow direction is indicated by an arrow on the EVAP canister purge valve. When the valve is installed, the flow direction can be checked by way of the position of the electric connector. The connector must point towards the intake manifold.

Check triggering of the EVAP canister purge valve.
1. Connect system tester.
2. In menu Drive links", select "Tank Vent". The EVAP canister purge valve must switch audibly.

Check voltage supply and leads.
1. Disconnect connector at EVAP canister purge valve.
2. Connect voltmeter (positive) to pin 1 of the connector and to ground.
3. Switch on ignition. Display: Battery voltage
4. Disconnect ECM connector.
5. Connect ohmmeter between ECM connector pin 61 and EVAP canister purge valve connector pin 2. Display: 0 - 5 ohms.

Check EVAP canister purge valve.
1. Disconnect hose from EVAP canister purge valve to intake system at EVAP canister purge valve.
2. Remove connector at EVAP canister purge valve.
3. Connect special tool 9160/1 to EVAP canister purge valve.
4. Generate vacuum of approx. 0.7 bar.

- The vacuum must not fall below 0.5 bar after 10 minutes.

Check hose between EVAP canister purge valve and intake system.
1. Undo hose at intake system.
2. Remove connector at EVAP canister purge valve.
3. Connect special tool 9160/1 to hose and generate a vacuum of approx. 0.7 bar.

- The vacuum must not fall below 0.5 bar after 10 minutes.

Check mixture throughput of fuel tank ventilation system.
1. Connect system tester.
2. Select "Tank vent in the menu "Short test".

NOTE: Fuel tank ventilation diagnosis must not yet have been performed.

3. After selecting fuel tank ventilation, press key 1 when the following display appears:

Please
Wait.

The following display now appears:

Tank Vent
B: Z: E:
DFRDTE: 0.000
DQSDTE: 0.0 kg/h.

Key to abbreviations:
B - Diagnosis condition flag
Z - Cycle flag
E - Error flag
The presence of the flags is indicated by an asterisk.

The following values must be attained in the test:
DFRDTE: >0.078 or or
DQSDTE: >/= 2.0 kg/h.

- The mixture throughput is too low if none of the three values is attained.

- Check all hoses for restrictions.
- Check four-fold distributor between EVAP canister purge valve and throttle housing for restrictions.
- Check evaporative emission (EVAP) canister.