P0440

Evaporative Emission (EVAP) System:

Evaporative Emission (EVAP) System (continued):

Evaporative Emission (EVAP) System:

Circuit Description

The evaporative 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 cap
^ Tank Pressure Control Valve
^ Evaporative emission canister
^ Purge lines
^ EVAP canister purge valve

The evaporative leak detection diagnostic strategy is based on applying vacuum to the Evaporative Emissions (EVAP) system and monitoring vacuum decay. The PCM monitors vacuum level via the fuel tank pressure sensor input. At an appropriate time, the EVAP canister purge valve and the EVAP vent solenoid are turned "ON," allowing engine 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 is indicated with DTC P0440. This can be caused by the following conditions:

^ Faulty or loose fuel cap
^ Damaged or leaking EVAP purge line
^ Damaged or leaking EVAP vent hose
^ Damaged or leaking fuel tank vapor line
^ Leaking or faulty EVAP canister purge valve
^ Leaking or faulty EVAP tank pressure control solenoid vacuum valve
^ Leaking or faulty EVAP vent solenoid
^ Leaking or faulty EVAP canister
^ Leaking fuel sender assembly O-ring
^ Leaking fuel tank or fuel filler neck
^ Faulty tank pressure control valve
^ Fuel level sensor malfunction
^ Fuel tank pressure sensor malfunction

Any of the above conditions can set DTC P0440.

Conditions for Running the DTC

^ Engine coolant temperature between 70°C (158°F) and 110°C (230°F).
^ Intake air temperature between -10°C (14°F) and 50°C (122°F).
^ Barometric pressure greater than 75 kPa.
^ Calculated Mass Air Flow (MAF) greater than 5 - 30 g/sec.
^ Fuel tank level is between 25 and 75%.

Conditions for Setting the DTC
^ Fuel tank pressure change.
^ Purge accumulation time greater than 200 seconds.

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 one ignition cycle in which the diagnostic runs without a fault.
^ Freeze Frame information and the history DTC will clear after one ignition cycle in which the diagnostic runs without a fault.
^ DTC(s) can be cleared by using a scan tool or by disconnecting the PCM battery feed.

Diagnostic Aids

Check for the following conditions:
^ EVAP canister
^ EVAP canister purge valve
^ EVAP canister vent solenoid
^ EVAP tank pressure control solenoid vacuum valve
^ Tank pressure control valve
^ Missing or damaged O-rings at EVAP canister fuel vapor and purge line fittings.
^ Cracked or punctured EVAP canister.
^ Damaged or disconnected source vacuum line. EVAP purge line. Vent hose or fuel tank vapor line.
^ Poor connection at PCM. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
^ Damaged harness. Inspect the wiring harness to the EVAP vent solenoid, EVAP canister purge valve, EVAP tank pressure control solenoid vacuum valve and the fuel tank pressure sensor for an intermittent open or shorted circuit.
^ Pinched or plugged vacuum source. EVAP purge. fuel tank vapor line. or signal vacuum to tank pressure control valve. Verify that the lines are not restricted.

If 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 last set.

If any wiring repairs need to be made, Refer to Repair Procedures in Diagrams.

Test Description

Number(s) below refer to the step number(s) on 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 other EVAP DTC(s) are set (except DTC P0455), go to the appropriate DTC table.

6. This step checks the operation of the EVAP tank pressure control solenoid vacuum valve. Output controls can be found on the scan tool under Misc. Test.

9. If the test light illuminates during this test the problem may be the result of the control circuit shorted to ground. This will keep the EVAP tank pressure control solenoid vacuum valve open and causing the system to fail.

10. This step checks the EVAP canister purge valve for leakage.

13. This step checks the operation of the EVAP canister vent solenoid. Output controls can be found on the scan tool under Misc. Test.

16. Determines whether or not the EVAP system is sealed sufficiently to be pressurized. If not, the leak must be located and corrected before continuing with diagnosis.