P0455

EVAP System:

EVAP System Leak Detected:

P0455- EVAP SYSTEM LEAK DETECTED
The evaporative emission (EVAP) system is used to store fuel vapors as to reduce the amount of unburned fuel from escaping into the atmosphere. The EVAP system consists of the EVAP canister. fuel tank pressure (FTP) sensor, EVAP lines and hoses, EVAP purge solenoid (normally closed). EVAP service port, EVAP vent solenoid (normally open) and fuel tank. The ECM monitors the EVAP system for circuit faults in the EVAP purge solenoid, EVAP vent solenoid and FTP sensor circuits. The ECM also monitors the EVAP system for leaks (between EVAP vent and EVAP purge solenoid). When certain conditions have been met, the ECM will perform an EVAP diagnostic test at idle with no vehicle speed. which will require a five consecutive phase (A, B, C, D and F) test. 1)TC P0445 will set if a vacuum cannot be pulled on the EVAP system during Phase D of the EVAP diagnostic system test indicating a large EVAP system leak or insufficient vacuum to the EVAP purge solenoid.

DTC PARAMETERS
DTC P0455 will set it fuel tank pressure cannot be pulled lower than 2.02 volts [4.50mmHg (-2.41 inH2O)] during phase D of the EVAP diagnostic system test indicating a large EVAP leak when:
^ Condition exists for 15 seconds or no change is detected for 4 seconds
^ EVAP purge solenoid is commanded to a 20% duty cycle
^ EVAP vent solenoid is commanded On Engine is at idle
^ Vehicle speed = 0 mph
^ Engine load less than 35%
^ MAP is less than 40 kPa
^ Battery voltage is greater than 11.0 volts
^ Start-up ECT is between 8°C and 75°C (460 and 167 °F)
^ IAT is between 8°C and 50°C (460 and 122°F)
^ Long term fuel trim cells learned (if not learned. engine must run longer than 16 minutes and 45 seconds)
^ Fuel level between 6 and 48L (1.6 and 12.7 gallons)
^ No ECT. EVAP purge solenoid, EVAP vent solenoid, fuel tank pressure, idle speed, HO2S, throttle actuator, TP sensor or vehicle speed DTCs have been set.

DTC P0455 diagnostic runs once during phase D of the EVAP diagnostic test once per ignition cycle.

If an EVAP diagnostic test is aborted due to changing enable criteria, the ECM will attempt to rerun the EVAP diagnostic test up to three times per ignition cycle.

P0455 is a type B DTC

DIAGNOSTIC AIDS

IMPORTANT: If any EVAP system DTC is set, EVAP special functions on Scan tool will not be allowed. Clear DTCs before performing these tests.

IMPORTANT: The ECM uses the fuel tank pressure sensor to detect the pressure of fuel vapor in the fuel tank during all parts of the EVAP diagnostic system test. Make sure the fuel tank pressure sensor is not skewed by verifying FUEL TANK PRESS. SENSOR on Scan tool is between 2.35 and 2.85 volts with ignition On and engine Off and fuel cap removed.

Make a visual inspection for a large leak of the EVAP system. Use the EVAP System Tester to locate the large leak. Follow operating instructions in the EVAP system description at the end of this section.

Refer to "EVAP System Description" procedure at the end of this section for a complete EVAP diagnostic test description.

Possible causes of a large EVAP leak:
^ Fuel cap missing, incorrectly installed or leaking EVAP vent solenoid valve stuck open
^ EVAP purge solenoid stuck closed/blocked or lack of manifold vacuum to solenoid
^ EVAP line/hose connections disconnected/leaking
^ Fuel sender O-ring leaking
^ Fuel tank pressure sensor seal leaking

USE THE EVAP SYSTEM PICTURE, WHICH WILL POINT TO POSSIBLE LEAK AREAS.