P0456
P0456Evaporative Emission System Leak Detected (very small leak)
Diagnostic conditions
- Battery voltage between 10 V and 16 V
- Engine must cool down by at least 42 °K in the time that elapses between stopping and restarting engine
- Intake air temperature between 5 °C and 95 °C
- Variations of intake air temperature less than 12 °K
- Vehicle is travelling with longer partial load share (3 - 150 km/h)
- Engine temperature higher than 5 °C
- Diagnosis only runs below 2400 m above sea-level
- No P0441, P0444, P0445 (EVAP canister purge valve) or P0446, P0447, P0448 (EVAP canister shutoff valve) faults in memory
- No P0455 tank system (major leak) and P0442 (small leak) faults in memory
- No P2400, P2401, P2402 (leakage diagnosis pump) fault in memory
- No P2403 and P2404 (reed switch) fault in memory
Possible cause of fault
- Tank cap not tightened correctly or faulty
- Mechanical fault in EVAP canister purge valve (does not close fully)
- Leakage diagnosis pump leaking internally (membrane) or externally
- Mechanical fault in EVAP canister shutoff valve (does not close fully when power is supplied)
- EVAP canister shutoff valve connections leaking
- Tank system (including pipes) leaking
Affected terminals
-
Diagnosis/troubleshooting
NOTE:
- This fault code can also imply an internal leak within the tank system. In such a case, there would be no external leak despite the detection of a leaking tank. We strongly recommend to follow to the word the work instructions given in the table below.
- The fuel tank leak test for the Cayenne is carried out with approx. 20 mbar overpressure in the tank. This overpressure is built up by the leakage diagnosis pump and is evaluated using an integrated reed contact. The pump work is performed by a spring, which is stretched over a membrane by the vacuum from the intake manifold (or supply tank).
- There may be several smaller leaks that in combination correspond to the leak detected here which has a diameter of roughly 0.5 - 1 mm.
- The diagnostic conditions can also be 'forced' by performing the "Leakage Diagnosis" short test using the 9588 Porsche System Tester II.
DANGER:
- Danger of toxication through petrol.
- Inhaling vapours can lead to irritation of the mucous membranes and eyes.
- It represents a serious risk to health when inhaled, touched or swallowed over longer periods.
- Wear a breathing mask with active charcoal filter; do not breathe in any fuel vapours.
- Wear protective gloves that are fuel-resistant.
- Only work on the fuel system in well-ventilated locations.
- Before opening fuel lines or fuel hoses, relieve the fuel pressure.
- Collect escaping fuel; absorb it if necessary with a suitable binding material and dispose of properly
- Pay attention to cleanliness when working on the fuel system.
DANGER:
- Risk of fire and explosion when handling petrol.
- Keep clear of ignition sources.
- Do not smoke.
- Do not carry out welding or grinding work in the immediate vicinity (naked flame and flying sparks).
- Prevent escaping fuel from coming into contact with hot engine components.
- Avoid electric discharges in the vicinity of escaped fuel.
- Secure the vehicle, e.g. with a warning sign.
- Change any clothing soaked with fuel immediately.
- In the event of a fire, use C02 or dry powder fire extinguishers.
Evaporative Emission System Leak Detected (very small leak)
NOTE: The following troubleshooting contains, at the beginning and after every test step, the procedure for the respective short test. This is important to ensure confirmation that a fault has been removed.
1 - Disconnection point between vacuum line and vacuum accumulator in intake manifold and leakage diagnosis pump
2 - Disconnection point purge air line between EVAP canister shutoff valve and EVAP canister purge valve
3 - Disconnection point fuel supply line
9160/1 Mityvac II vacuum tester with pressure gauge
NOTE:
- During step 10 of the following table, tank system components are supplied with ground and vacuum.
- This ensures that during the subsequent external fuel tank leak test (step 11 of the following table) the leakage diagnosis pump and the EVAP canister shutoff valve close off the tank system.
