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P1456

Read the instructions below then start the fault diagnostic procedure.

Symptom: CHECK ENGINE. Possible smell of petrol. Possible faulty reading on the fuel gauge in MIU.

P1456


EVAP Small Leakage in System and malfunctional fuel level sensor.


Fault symptoms


• CHECK ENGINE.

• Possible smell of petrol.

• Possible faulty reading on the fuel gauge in MIU.


On-Board Diagnostics

Type of diagnosis:


- Once per driving cycle. Interrupted when fault criteria fulfilled or OK reported. Restarts next driving cycle.


Test 1, Stationary idling speed

Enable criteria:


- Run the engine at idling speed. Max one status change for brake light switch. Venting adaptation higher than 7%. Intake air pressure is at least 20 kPa lower than ambient pressure. The fuel volume in the tank is between 11 - 60 litres. The battery voltage is between 10 - 16 Volts. Tank pressure between -300 to +100Pa.

When the above criteria have been fulfilled for a duration of 100 ms, the diagnosis can be started. If the diagnosis is interrupted, the speed must be in excess of 45 km/h for 30 s before it can be re-started. The diagnosis is divided into three phases, A-C:

Phase A) Evaporation control Shut-off valve is activated (closes) and any venting is interrupted for 8 s. Monitor the tank pressure. A drop in pressure can indicate a leaking evap canister purge valve. A rise in pressure of more than 7 Pa/s may indicate fuel evaporation and the test should be stopped. If the rise in pressure is less than 7 Pa/s, phase A is completed and the diagnosis continues towards a pressure reduction.

Phase B) Pressure reduction Shut-off valve still closed, evap canister purge valve pulse ratio is set to 23-24.5 % until the tank pressure has reached -1500 Pa. The duration of the pressure reduction may not exceed 25 seconds.

Phase C) Retaining pressure Shut-off valve still closed, evap canister purge valve is closed. Monitor the tank pressure for approximately 10 seconds.


Test 2, Driving

Enable criteria:


- The following criteria must be fulfilled for a duration of 3 seconds before the diagnosis can be started: Speed between 70-130 km/h. Venting adaptation higher than -6%. Tank pressure is between -300 to +100 Pa. Intake air pressure is at least 20 kPa lower than ambient pressure. The fuel volume in the tank is between 11-60 litres. The battery voltage is between 10-16 Volts. The tank pressure gauge diagnostic should not have reported an incorrect value.

When the above criteria have been fulfilled for a duration of more than 3 seconds, the diagnosis can be started. The diagnosis should be stopped if the venting adaptation exceeds 6 %. If the diagnosis is interrupted, the speed must exceed 50 km/h for 1 minute before the diagnosis can be re-started. The diagnosis is divided into three phases, A-C.

Phase A) Evaporation control Shut-off valve is activated (closes) and any venting is interrupted for 10s. Monitor the tank pressure and stop the diagnosis if the pressure drops. A rise in pressure of more than 5 Pa/s may indicate fuel evaporation and the test should be stopped. If the rise in pressure is less than 5 Pa/s, phase A is completed and the diagnosis continues to phase B (pressure drop).

Phase B) Pressure reduction Shut-off valve still closed, evap canister purge valve pulse ratio is set to 40 % until the tank pressure has reached -2000 Pa. The duration of the pressure reduction may not exceed 23 seconds.

Phase C) Retaining pressure Shut-off valve is still closed and the evap canister purge valve closes. Monitor the tank pressure for approximately 14 seconds.


Fault criteria:


- Phase A) If evaporation control shows that the pressure rises by more than 5 Pa/s, the diagnosis should be stopped due to substantial fuel evaporation. In order to re-start the diagnosis, the car must be moving. If the increase in pressure is under 5 Pa/s, the diagnosis continues to phase B.

- Phase B) Pressure reduction If it is not possible to reduce the pressure in three 8-second stages of approximately -500 Pa each, a large leak has been discovered. (24 s total)

- Phase C) Retaining pressure An increase in pressure indicates a small or large leak.


Fault code generation


- Diagnostic trouble codes are generated when the above fault criteria are fulfilled and the dependents are OK.

- Fuel level, reasonability diagnosis: Because fuel level is used as an enable criterion in certain diagnoses, the control module must know that the fuel level value is reasonable. This occurs in the following manner; Trionic receives the bus message ”Fuel level XX litres" from the MIU. Trionic monitors the value and knows that the fuel level value should sink while the car is being driven. There are several value filters in Trionic which help to avoid discrepancies such as sloshing in the tank or starting on a hill. The fuel level diagnosis can be seen as a support diagnosis; it reports no diagnostic trouble code but P0455 is normally set if the tank seal diagnosis reports a large leak for example. If, however, the tank seal diagnosis has reported the same fault at the same time as the fuel level diagnosis has reported a fault, P1455 is set instead.

- P0455, P1455 are set if faults are reported during Phase B

- P0442, P0456, P1442 or P1456 are set if faults are reported during Phase C.

Diagnosis is intended to detect leaks as small as 0.5 mm2 and may require 7 driving cycles before generating a DTC. If the DTC is detected, it is vital that correct fault diagnosis is performed. For final inspection, perform the diagnostic cycle 7 times and then read the fault codes to ensure the DTC has not been generated.


Dependents:


- P0444, P0445, P0501, P0502, P0506, P0507, P1444, P1445, P1576 and P1577.


OK report:


- Test 1 or Test 2 performed once and fault criteria not fulfilled.

Note

Diagnostic trouble codes P0455 and P1455 are erased immediately after an OK report from the diagnosis.



Fault handling:


- Type III.


Diagnostic help

Fault diagnosis concerns a leak.

Functions in the diagnostic tool related to the fault:


• Diagnostic status for the diagnosis.

• Activate EVAP diagnosis.


For more information, see Fault diagnosis strategy for electronic systems .