Fuel Tank Ventilation System - Above Limit

P0440

Fuel Tank Ventilation System - Above Limit

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 (or EVAP canister) that retains the fuel vapors. When driving, air is drawn in through the EVAP canister and picks up the accumulated fuel vapors and feeds them to the combustion process.

Diagnosis conditions
- Engine idling
- Vehicle speed = 0 km/h
- Oxygen sensing system active
- Time elapsed after engine start-up [>] 990 sec.
- No secondary air injection
- Engine load [<] 1.9 ms
- Air mass [<] 30 kg/h
- Engine temperature at time of start-up ≥ -15° C
- Engine temperature ≥ 60° C
- The vehicle must not be at an altitude of above 2448 m
- No faults in: Throttle position sensor, idle air control, vehicle speed, EVAP canister purge valve output stage, idle air control valve, mass air flow sensor, load sensing, voltage supply and engine temperature

NOTE: Fuel tank ventilation can be activated with the Porsche System Tester 2 in the Short test menu.

P0440:

NOTE: The EVAP canister purge valve is very sensitive to contamination. If the lines to the EVAP canister have to be detached, the outside of the canister must be cleaned beforehand.

System Overview







Wiring Diagram







Diagnosis Procedure







1 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. The arrow must point towards the intake manifold.

2 Check triggering of EVAP canister purge valve.

1. Connect Porsche System Tester 2.
2. In the Drive links menu, select EVAP canister purge valve.
The EVAP canister purge valve must switch audibly.

3 Check voltage supply and wiring.

1. Remove connector of EVAP canister purge valve.
2. Connect voltmeter (positive) to pin 1 of the connector and to ground.
3. Switch on the ignition.
Display: battery voltage

4. Connect special tool 9616 to wiring harness.
5. Connect ohmmeter to pin 61 and EVAP canister purge valve connector, pin 2.
Display: 0 - 5 ohms

4 Check EVAP canister purge valve.

1. Disconnect hose from EVAP canister purge valve to intake system at EVAP canister purge valve.
2. Remove connector of 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.

5 Check hose line between EVAP canister purge valve and air intake system.

1. Undo hose at intake system.
2. Remove connector of 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.