P0455

DTC P0455

SYSTEM DESCRIPTION




The evaporative emission (EVAP) system is used to store fuel vapors to reduce the amount of unburned fuel from escaping into the atmosphere. The EVAP system consists of the EVAP canister, the fuel tank pressure (FTP) sensor, the EVAP lines and hoses, the EVAP canister purge solenoid value which is normally closed, the EVAP service port, the EVAP canister vent solenoid valve which is normally open, the fuel tank, and the powertrain control module (PCM). The PCM monitors the EVAP system for circuit faults in the FTP sensor, the EVAP canister purge solenoid valve and the EVAP canister vent solenoid valve circuits. The PCM also monitors the EVAP system for small and large leaks. During the DTC P0455 diagnostic, the PCM monitors the FTP sensor for an atmospheric pressure reading when all of the DTC parameters have been met with the engine running. The PCM will then command the EVAP canister vent solenoid valve ON which is a closed valve, and command the EVAP canister purge solenoid valve to a fixed duty cycle, with the engine running. The PCM will let the pressure drop in the fuel tank for a certain length of time after which it will turn OFF the EVAP canister purge solenoid value. DTC P0455 sets when a certain vacuum in the fuel tank could not be achieved due to a large leak or a lack of vacuum source.

CONDITIONS FOR RUNNING THE DTC
- DTCs P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0122, P0123, P0125, P0131, P0132, P0133, P0134, P0135, P0452, P0453, P0502, P0503, P0601, P0602, P1621 are not set.
- The EVAP canister vent solenoid valve is commanded ON, closed.
- The EVAP canister purge solenoid valve is commanded to a fixed duty cycle.
- The engine is running.
- The fuel tank level is between 15-85 percent.
- The barometric pressure (BARO) is more than 75 kPa.
- The engine coolant temperature (ECT) and the intake air temperature (IAT) at engine startup are between 4-30°C (39-86°F).
- The ECT and the IAT are within 8°C (15°F) of each other.
- The throttle position (TP) angle is between 7-35 percent.
- The vehicle speed is less than 113 km/h (70 mph).
- The DTC P0455 diagnostic runs once per ignition cycle after the above conditions have been met.

CONDITIONS FOR SETTING THE DTC
- If the FTP voltage is more than 1 volt during the DTC P0455 diagnostic test indicating a vacuum cannot be pulled on the EVAP system, DTC P0455 will set.
- The above condition exists for longer than 6 minutes and 40 seconds.

ACTION TAKEN WHEN THE DTC SETS
- The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
- The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
- The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
- A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
- Clear the MIL and the DTC with a scan tool.

DIAGNOSTIC AIDS
- The PCM uses the FTP sensor to detect the amount of vacuum pulled on the EVAP system during the leak diagnostic tests. Ensure that the fuel pressure sensor is not skewed by verifying the FTP sensor on the scan tool is between 2.35-2.85 volts with the ignition ON and the fuel cap removed.
- If this test fails, a warm test will be performed and can only pass, not fail, a diagnostic test. The purpose of this test is to keep the malfunction indicator lamp (MIL) OFF during the initial test if the customer starts the vehicle with the fuel cap off.
- Visually inspect for a large leak in the EVAP system. Locate the leak with the J 41750 OBD II/Enhanced Emissions Testing Equipment (Cart Only).
- The following are possible causes of a large leak:
- The fuel cap is missing, is incorrectly installed or is leaking.
- The EVAP canister vent solenoid valve is stuck open.
- The EVAP canister purge solenoid valve is stuck closed or is blocked.
- The EVAP canister vent hose is loose or is damaged.
- The EVAP canister is leaking.
- The fuel sender assembly O-ring is leaking.
- The fuel tank or filler neck is leaking.
- A condition may exist where a leak in the EVAP system only exists under a vacuum condition. By using the scan tool Purge/Seal function to create a vacuum, seal the system and observe the fuel tank pressure (FTP) parameter for vacuum decay, this type of leak may be detected.

TEST

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Steps 24-35: