P0440

Diagnostic Chart (Part 1 Of 5):

Diagnostic Chart (Part 2 Of 5):

Diagnostic Chart (Part 3 Of 5):

Diagnostic Chart (Part 4 Of 5):

Diagnostic Chart (Part 5 Of 5):

Schematic:

CIRCUIT DESCRIPTION
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 P0440 sets.

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

CONDITION FOR RUNNING THE DTC
^ The Engine Coolant Temperature is between 70°C and 110°C (158°F-230°F)
^ The Intake Air Temperature is between -7°C and +70°C (19°F-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 and 3,000 RPM (A/T), or 1,000 and 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 run.

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
^ The MIL turns off after 3 consecutively passing trips without a fault present.
^ A 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
A DTC P0440 is more likely to set during city driving. Avoid operating the vehicle for long periods on the highway when validating DTC P0440.

The EVAP purge diagnostic checks for many of the faults that can cause DTC P0440 to set. If the EVAP Purge test passes the cause of the DTC P0440 is probably intermittent. Clear the DTCs. Road test the vehicle while monitoring the EVAP Purge in the MIL/System Status selection under System Information on the scan tool. When the EVAP Purge indicates complete with a YES status, check for DTC P0440 under Last Test Failed. If there is no DTC P0440 indicated, the DTC is intermittent and the purge system diagnostic is indicating OK at this time.

Check for any of the following conditions:
^ 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 level sensor can cause DTC P0440 to set.
^ A faulty or erratic fuel tank pressure sensor can cause DTC P0440 to set.
^ A faulty EVAP canister purge valve
^ A faulty EVAP canister vent valve
^ A faulty EVAP tank pressure control vacuum valve

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

If a 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. 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.

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 any of the following conditions:
^ Any backed-out terminals
^ Any improper mating of terminals
^ Any broken electrical connector locks
^ Any improperly formed or damaged terminals
^ Any faulty terminal-to-wire connections
^ Any physical damage to the wiring harness
^ A broken wire inside the insulation
^ Any corrosion of the electrical connections, the splices, or the terminals

If the DTC P0440 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
The numbers below refer to the step numbers in the diagnostic table.
1. The Powertrain OBD System Check 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.
2. If any EVAP diagnostic trouble codes Other than DTC P0455 are set, diagnose those DTCs first.
6. This step checks the operation of the pressure control vacuum valve of the EVAP tank. The output control of the pressure control vacuum valve is disabled by the PCM when any DTCs are stored and when engine speed is indicated.
9. This step checks the control circuit of the pressure control vacuum valve. A short to ground will keep the pressure control vacuum valve open and cause the system to fail. The output control of the pressure control vacuum valve 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. A plugged or leaking EVAP canister surge tank may prevent vacuum from reaching the EVAP canister purge valve.
11. 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.
15. 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.
18. 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.
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 determines whether the malfunction that caused 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 P0440 diagnostic has not yet run. When 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. 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.