P0455

LEAKAGE IN THE PURGE SYSTEM





Fault Symptoms.
CHECK ENGINE lamp (MIL) on.
Possibly a smell of petrol.

Conditions For Diagnosis.
^ Inlet temperature above -6.7°C.
^ 1,000 seconds after starting.
^ Engine temperature above -6.7°C.
^ Vehicle speed 0 km/h.
^ Idling.

Conditions For Diagnostic Trouble Code Generation.
P0455 (large leakage):
When the supply air for the evaporative emission canister is shut off and purging is active, no drop in tank pressure occurs.

P0442 (small leakage):
When the supply air for the evaporative emission canister is shut off and purging is active, a drop in tank pressure occurs.

When purging is subsequently stopped, however, the pressure rises too quickly.





Diagnostic Help.
The diagnostic trouble code indicates a leak in one of the following components:
^ Fuel filler cap, e.g. not screwed down properly or damaged seal.
^ Filler pipe or breather pipe.
^ Petrol tank, above fuel level.
^ The line from the roll-over valve to the evaporative emission canister.
^ Evaporative emission canister.
^ Evaporative emission canister shut-off valve.
^ The line from the evaporative emission canister to the purge valve.
^ Purge valve.

The evaporative emission canister's purge valve can be activated with the ISAT scan tool.
- Select "ACTIVATE".
- Select "EVAP SHUTOFF VALVE".

A tank pressure reading can be obtained with the ISAT scan tool.
- Select "READ FUNCTIONS".
- Select "TANK PRESSURE".

The diagnostic trouble code will also be generated if a break in the circuit to the evaporative emission canister's shut-off valve occurs and in the event of an erroneous, constant value from the fuel tank pressure sensor.

Check The Wiring.
Intermittent faults may occur as a result of temporary short circuits and breaks in the wiring. Jiggle the wiring at several points and in different directions to ascertain whether the wiring harness, including any connectors, is causing the trouble. Observe the multimeter, ISAT scan tool or test lamp while doing this.





Diagnostic Procedure.
1. Check the fuel filler cap

- If possible, check whether the filler cap was screwed down properly when the fault was detected.
- Check whether the filler cap is screwed on properly.
- Check the fuel filler cap's seal and sealing surfaces.

Is the filler cap OK?
YES: Continue with point 2.
NO: Rectify the fault and continue with point 5.

2. Check for fuel leakage

Fill up with fuel right up to the filler pipe. Carry out a visual check to see whether petrol is leaking from the tank, filler pipe or breather pipe.

Any leakage?
YES: Rectify the fault and continue with point 5.
NO: Continue with point 3.





3. Check the purge valve

- Check that the purge valve is closed when it receives no current (zero voltage) and opens when current is applied to it.

Is the purge valve OK?
YES: Continue with point 4.
NO: Change the valve and continue with point 5.





4. Check the purging circuit

- Turn the ignition switch to the OFF position.
- Unplug the connector from the evaporative emission canister's shut-off valve.
- Connect the shut-off valve (male connector) to the battery.
- Connect a pressure/vacuum pump and pressure gauge to the evaporative emission canister`s hose.
- Remove the fuel filler cap and cover the hole in the roll-over valve.
- Reduce the pressure to 0.1 bar by means of the pressure/vacuum pump.

The pressure must not be allowed to rise.

Did the pressure rise ?
YES: The leakage is confined to the evaporative emission canister, including connected lines, or the shut-off valve. Rectify the fault and continue with point 5.
NO: Change the fuel filler cap and continue with point 5.





5. Final check

IMPORTANT: Fault diagnosis ray be interrupted if petrol evaporation is excessive or if the evaporative emission canister is saturated. For fault diagnosis to be possible, proceed as follows:

^ Run the engine at 4000 rpm for two minutes.
^ Switch off the engine and wait for 10 seconds.
^ Start the engine and repeat the final check.

The ISAT scan tool is used to activate diagnosis of the EVAP system. The following conditions must be fulfilled for diagnosis to be possible:
^ Engine running at idling speed.
^ Closed loop active.
^ Vehicle speed 0 km/h.

Carry out diagnosis:
- Connect the ISAT Scan Tool.
- Clear the fault codes.
- Select "INITIATE".
- Select "EVAP DIAGNOSIS".
- Wait for about two minutes or until the ISAT scan tool reads "READY".
- Obtain a readout of the diagnostic trouble code.

Has the diagnostic trouble code recurred?
YES: Continue at "Before Replacing a Control Module". Component Tests and General Diagnostics
NO: The steps taken to rectify the fault were correct.