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P0440

CIRCUIT DESCRIPTION
The DTC P0440 Evaporative Emission (EVAP) System diagnostic monitors the EVAP system components for correct operation. The 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 solenoid, allowing engine manifold pressure (vacuum) to draw a small vacuum on the entire evaporative emission system. If a sufficient vacuum cannot be sustained over a given period of time, a small leak (or a malfunction) is suspected and a DTC P0440 sets. The Evaporative Emission (EVAP) system as defined by federal regulation includes the following components:
^ Fuel tank
^ EVAP vent solenoid
^ Fuel tank pressure sensor
^ Fuel pipes and hoses
^ Vapor lines
^ Fuel filler cap
^ Fuel tank pressure control valve
^ Evaporative emission canister
^ Purge lines
^ EVAP canister purge valve

CONDITION FOR RUNNING THE DTC
^ The engine coolant temperature is between 70°C and 110°C (158°-230°F)
^ The intake air temperature is between -7°C and +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 between 1,000-3,000 RPM (A/T), or 1,00-3,500 RPM (M/T).

CONDITIONS FOR SETTING THE DTC
A fuel tank pressure change indicates the EVAP purge accumulation time is more than 360 seconds.

The diagnostic may take up to 20 minutes to complete.

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

CONDITIONS FOR CLEARING THE MIL/DTC
^ The MIL will turn OFF after three consecutive drive cycles without a fault present.
^ A DTC will clear after 40 consecutive warm-up cycles without a fault.
^ DTCs can be cleared by using a scan tool or by disconnecting the PCM battery feed.

DIAGNOSTIC AIDS
A DTC P0440 is more likely to set during city driving. Avoid operating the vehicle for long periods on the highway when validating a DTC P0440.

If a DTC P0440 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 P0440 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

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

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 P0440 is intermittent, driving the vehicle under the following conditions can verify whether the fault is present. Perform the scan tool Clear DTC Information function. Road test the vehicle while monitoring the DTC P0440 diagnostic on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P0440 appears in the Not Ran Since Code Cleared list, the P0440 diagnostic has not yet run. When the DTC P0440 does not appear in the Not Ran Since Code Cleared list, the P0440 diagnostic has run. If the MIL is NOT ILLUMINATED, and there is no PENDING DTC Status in DTC Information, the P0440 diagnostic has passed. DTCs MUST BE CLEARED in order to view the CURRENT STATUS of the Not Ran Since Code Cleared list. DO NOT FORGET that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for CURRENT or PENDING status, in order to determine the outcome of the diagnostic test involved.

If you duplicate the DTC P0440, 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 1-3:




Steps 4-9:




Steps 10-16:




Steps 17-24:




Steps 25-36:




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 to 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.
2. If any other EVAP DTCs except a DTC P0455 are set, diagnose those DTCs first.
6. This step checks the operation of the EVAP tank pressure control solenoid valve. The EVAP tank pressure control solenoid valve output control is disabled by the PCM when any DTCs are stored and when engine speed is indicated.
9. This step checks the EVAP tank pressure control solenoid valve control circuit. A short to ground will keep the EVAP tank pressure control solenoid vacuum valve open and cause the system to fail. The EVAP tank pressure control solenoid valve output control is disabled by the PCM when any DTCs are stored and when engine speed is indicated.
10. This step checks the components that supply manifold vacuum to the EVAP canister purge valve.
11. This step checks the operation of the EVAP canister purge valve. The EVAP canister purge valve duty cycle control is disabled by the PCM when any DTCs are stored and when engine speed is indicated.
15. This step checks the operation of the EVAP canister vent solenoid. The EVAP canister vent solenoid output control is disabled by the PCM when any DTCs are stored and when engine speed is indicated.
18. This step checks the EVAP canister vent solenoid control circuit. The EVAP canister vent solenoid output control is disabled by the PCM when any DTCs are stored and when engine speed is indicated.
19. 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.
20. Use the ultrasonic leak detector in order to locate any leaks after pressurizing the EVAP system.
22. This step checks the EVAP canister for blockage or restrictions.
35. This step checks whether the malfunction that caused the DTC P0440 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 P0440 diagnostic can be monitored on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If DTC P0440 appears in the Not Ran Since Code Cleared list, the DTC P0440 diagnostic has not yet run. When DTC P0440 does not appear in the Not Ran Since Code Cleared list, the DTC P0440 diagnostic has run. If the MIL is NOT illuminated and there is no Pending DTC Status in DTC Information, the DTC P0440 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status in order to determine the outcome of the diagnostic test involved.
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