P0455 (W/ ORVR)

CIRCUIT DESCRIPTION
The DTC P0455 Evaporative Emission (EVAP) System Leak Detected diagnostic monitors the operation of the EVAP system. The Evaporative Emission (EVAP) control system leak detection diagnostic strategy is based on applying vacuum to the EVAP system and monitoring vacuum decay. The Powertrain Control Module (PCM) monitors the vacuum level via the fuel tank pressure sensor input. The PCM turns ON the EVAP canister purge valve and the EVAP vent valve, allowing the engine manifold pressure to draw a small vacuum on the entire EVAP system. If sufficient vacuum cannot be sustained over a given period of time, a small leak or a malfunction is suspected and DTC P0455 sets. The EVAP system used with this powertrain is part of an On-board Refueling Vapor Recovery (ORVR) fuel system.

The EVAP system as defined by federal regulation includes the following components:
^ Fuel tank
^ EVAP canister vent valve
^ Fuel tank pressure sensor
^ Fuel pipes and hoses
^ Vapor lines
^ Fuel filler cap
^ Fuel tank pressure control valve
^ EVAP canister
^ Purge lines
^ EVAP canister purge valve

CONDITION FOR RUNNING THE DTC
^ The engine coolant temperature is 70-110°C (158-230°F)
^ The intake air temperature is -7 to +70°C (19-158°F).
^ The Barometric Pressure (BARO) is more than 75 kPa.
^ The fuel tank level is less than 75 percent.
^ The engine is operating in Closed Loop.
^ The engine speed is 1,00O-3,000 RPM (A/T), or 1,000-3,500 RPM (M/T).

CONDITIONS FOR SETTING THE DTC
The difference between the maximum internal pressure of the fuel tank and the minimum fuel pressure is less than the specified value.

The diagnostic may take up to 20 minutes to complete.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM illuminates the Malfunction Indicator Lamp (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with the fault active.
^ The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer.

CONDITIONS FOR CLEARING THE MIL/DTC
^ MIL turns off after 3 consecutively passing trips without a fault present.
^ History DTC clears after 40 consecutive warm-up cycles without a fault.
^ Perform the scan tool Clear DTC Information function in order to clear the DTC.

DIAGNOSTIC AIDS
Check for any of the following conditions:
^ An incorrect type fuel filler cap
^ A cracked or punctured EVAP canister
^ A damaged or disconnected source vacuum line, EVAP purge line, vent hose, or fuel tank vapor line
^ A faulty or erratic fuel tank pressure sensor can cause DTC P0455 to set.

For functional checks of the components listed above, refer to Evaporative Emission (EVAP) Control System Diagnosis (W/O ORVR) or Evaporative Emission (EVAP) Control System Diagnosis (with ORVR). Component Tests and General Diagnostics Component Tests and General Diagnostics

If a DTC P0455 is intermittent, driving the vehicle under the conditions outlined in the Inspection/Maintenance (I/M) section can verify whether the fault is present. Refer to Inspection/Maintenance (I/M) Evaporative Emission (EVAP) System Set Procedure. I/M Evaporative Emission (EVAP) System Set Procedure

A faulty or erratic fuel level sensor can cause DTC P0455 to set. Use the scan tool in order to check the operation of the fuel level sensor. If the accuracy of the fuel level sensor is suspect, refer to DTC P0461. P0461

An intermittent malfunction may be caused by a fault in any of the EVAP control system electrical circuits. Inspect the wiring harness and components for an intermittent condition. Refer to Intermittent Conditions. Intermittent Conditions

If the DTC P0455 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.

TEST DESCRIPTION

Steps 1-5:

Steps 6-12:

Steps 13-19:

Steps 20-31:

The numbers below refer to the step numbers in the diagnostic table.
1. The Diagnostic System Check-Computers and Control Systems prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
3. This step checks the operation of the FTP sensor. If the FTP sensor does not indicate near zero pressure when the fuel filler cap is removed, the FTP sensor or circuit might be faulty. The FTP sensor can be checked by using the diagnostics in DTC P0450.
5. This step uses tools from the EVAP pressure/ purge cart diagnostic station, in order to determine whether EVAP control system is sealed sufficiently to be pressurized. Any leak that is found must be located and repaired before continuing with the diagnosis.
8. This step checks the components that supply manifold vacuum to the EVAP canister purge valve.
9. This step checks the operation of the EVAP canister purge valve. The duty cycle control of the EVAP canister purge valve is disabled by the PCM when any DTCs are stored and when engine speed is indicated.
12. This step checks the operation of the EVAP canister vent valve. The output control of the EVAP canister vent valve is disabled by the PCM when any DTCs are stored and when engine speed is indicated.
16. This step checks the control circuit of the EVAP canister vent valve. The output control of the EVAP canister vent valve is disabled by the PCM when any DTCs are stored and when engine speed is indicated.
30. This step determines whether or not the malfunction that caused DTC P0455 is still present. Driving the vehicle under these conditions will verify whether the fault is present. After performing the scan tool Clear DTC Information function, the DTC P0455 diagnostic can be monitored on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If DTC P0455 appears in the Not Ran Since Code Cleared list, the P0455 diagnostic has not yet run. When DTC P0455 does not appear in the Not Ran Since Code Cleared list, the P0455 diagnostic has run. If the MIL is NOT illuminated and there is no Pending DTC Status in DTC Information, the P0455 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. The DTC Information screen must be checked for Current or Pending status in order to determine the outcome of the diagnostic test involved.