P1456

P1456 00

EVAP System, Fuel Level Sesor Failure And Very Small Leak Detected







Fault symptom
Check Engine

On-board diagnosis

Type of diagnosis:
Once per driving cycle. Stopped when fault criteria are fulfilled or OK reported.

Enable criteria:
Phase 1:
- The diagnosis is performed by closing the shut-off valve and opening the EVAP canister purge valve while the tank pressure is being registered. The pressure should then drop.

Phase 2:
- Bleeder valve closed; pressure increase in Pa/s calculated. Pressure must not rise too much.

Diagnostics can be carried out under 4 different operating conditions:
- After cold start while stationary.
- After cold start while driving.
- After warm start while stationary.
- After warm start while driving.

NONE of the following DTCs must be detected:
- P0117, P0118
- P0444, P0445
- P0451, P0452, P0453
- P0498, P0499
- P0501
- P0685, P0686, P0687

Diagnostics uses different calibration data for various operating conditions. Several conditions can interrupt diagnostics. After starting from cold, diagnostics restarts immediately if the vehicle speed exceeds 0 km/h. After warm start, a speed of over 44 km/h is required for a specific period of time before diagnostics restart.

Normally, the diagnosis takes 5 minutes with the engine idling if the intake temperature is above +15 degree C.

Fault criteria:
Pressure increase during phase 2 has been calculated and compared with fuel level in the tank. The pressure increase indicates a small leak; a hole with a diameter of 0.5 - 1.0 mm.
A fuel level sensor fault has been detected at the same time, which makes the EVAP diagnosis unreliable.

Dependent
None

System reaction to a fault:
None

OK report:
Diagnostics carried out without fault reported.

Fault handling:
Type III
(See Description of On-Board Diagnostics/Fault handling III, "Other emission-related components and functions" for more information.)

Checking the wiring harness
Move the wiring harness at several spots and in several directions to reveal intermittent breaks and short-circuits. Check switches, connectors and crimp connections for oxidation, retracted pins and pin clamping force.

Diagnostic help
In case of a fault in the sensor, the diagnosis will take 40 litres as a substitute value. When the EVAP diagnosis result has normalized above the fuel level, a fault may result even though there is no leak. Diagnose the fuel level sensor first and then check the EVAP system.