DTC Advanced Diagnostics: P0455
DTC P0455:Evaporative Emission (EVAP) System Large Leak Detected

General Description

The evaporative emission (EVAP) system monitor detects leaks in the fuel supply system by inducing and utilizing negative pressure in engine idle and vehicle OFF (LOCK) mode. This monitor is also used for diagnosing both the EVAP canister purge valve and EVAP canister vent shut valve for rationality malfunctions. Fuel that evaporates from the fuel canister gets stored in the EVAP canister. The evaporated fuel trapped in the EVAP canister is occasionally flushed at the appropriate engine operating conditions into the intake manifold via the EVAP canister purge valve. The EVAP canister vent shut valve isolates the evaporative system from ambient air. Several steps are taken to detect for leakage in the fuel supply system. If the difference between the fuel tank pressure and its reference (start) value during vacuum build-up is a specified value during vacuum build-up, the powertrain control module (PCM) detects a malfunction and stores a DTC.

Monitor Execution, Sequence, Duration, DTC Type
Execution
Once per driving cycle
Sequence
None
Duration
0.5 second or more
DTC Type
Two drive cycles, MIL on

Enable Conditions
General enable conditions to trigger EVAP system monitor
Condition
Minimum
Maximum
Elapsed time after starting the engine
9 minutes 10 seconds
–
Elapsed time since the last canister purging
–
30 seconds
Outside air temperature
32 °F (0 °C)
103.6 °F (39.8 °C)
Initial engine coolant temperature
[ECT Sensor 1]
32 °F (0 °C)
113 °F (45 °C)
Barometric pressure [Baro Sensor]
74 kPa (555 mmHg, 21.9 inHg)
–
Fuel tank pressure
-4 kPa (-30 mmHg, -1.1 inHg)
4 kPa (30 mmHg, 1.1 inHg)
12 volt battery voltage [Battery]
10.7 V
16 V
Fuel level
0 L (0 US gal)
41 L (10.8 US gal)
Fuel feedback
Closed loop
Other
No refueling
Both EVAP canister vent shut valve and EVAP canister purge valve are commanded open for at least 20 seconds
No excessive ambient pressure change for at least 5 minutes

Canister purging
Condition
 
Other
Both EVAP canister vent shut valve and EVAP canister purge valve are commanded open

EVAP canister vent shut valve stuck check
Condition
 
Other
EVAP canister vent shut valve stuck in closed position has not been detected
EVAP canister vent shut valve is commanded open and EVAP canister purge valve is commanded closed

Pressure stabilization after purging
Condition
 
Other
Fuel tank pressure has stabilized after purging for at least 3 seconds within 10 seconds

Phase A: Compensation gradient determination
Condition
 
Other
EVAP canister vent shut valve is commanded open
EVAP canister purge valve stuck in open position has not been detected
No high evaporation condition
No condensation condition

Phase B: Vacuum build-up
Condition
Minimum
Maximum
FTP sensor
–
-15 hPa (-12 mmHg, -0.45 inHg)
Other
EVAP canister purge valve is commanded open
EVAP canister vent shut valve remains commanded closed
No large leakage fault was detected while vacuum build-up
[ ]: HDS Parameter

Malfunction Threshold
Either of the conditions occurs and should be driven at least 0.2 miles (300 m) with no refueling event has been detected:
The integrated purge mass flow is greater than 1.96007 g (0.0691395 oz) - 2.2 g (0.078 oz) and the difference between the fuel tank pressure and its reference (start) value during vacuum build-up is greater than -1 kPa (-7 mmHg, -0.2 inHg).
The integrated purge mass flow is greater than 4 g (0.15 oz) and the difference between the fuel tank pressure and its reference (start) value during vacuum build-up is greater than -1.5 kPa (-11 mmHg, -0.44 inHg).

Possible Cause
NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
EVAP system large leak

Confirmation Procedure
Operating Condition
1.
Start the engine and drive the vehicle for a while.
2.
Stop the vehicle and let it idle for 10 minutes.
Drive the vehicle in this manner only if the traffic regulations and ambient conditions allow.

Diagnosis Details
Conditions for setting the DTC
When a malfunction is detected during the first drive cycle, a Pending DTC is stored in the PCM memory. If the malfunction returns in the next (second) drive cycle, the MIL comes on and a Confirmed DTC and the freeze data are stored.

Conditions for clearing the DTC
The MIL is cleared if the malfunction does not return in three consecutive trips in which the diagnostic runs. The MIL, the Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool Clear command.