P0440

Wiring Diagram:

Circuit Description
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 cap
^ Fuel 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 EVAP system and monitoring vacuum decay. The PCM monitors the 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 the DTC P0440. The DTC P0440 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 fuel tank pressure control valve
^ Fuel level sensor malfunction
^ Fuel tank pressure sensor malfunction
Any of the above conditions can set DTC P0440.

Conditions for Setting the DTC
Fuel tank pressure change:
^ Engine coolant temperature between 70°C (158°F) and 110°C (230°F).
^ Intake air temperature between -7°C (19°F) and 70°C (158°F).
^ Barometric pressure greater than 75 kPa.
^ Engine speed between 1,000 and 3,000 RPM (A/T), 1,000 and 3,500 RPM (M/T).
^ Fuel tank level is less than 75%.
^ Purge accumulation time greater than 360 seconds.
Diagnostic may take up to 20 minutes to run.

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.
^ DTC(s) can be cleared by using a scan tool or by disconnecting the PCM battery feed.

Diagnostic Aids
Check for problems in any of the following components:
^ EVAP canister
^ EVAP canister purge valve
^ EVAP canister vent solenoid
^ EVAP tank pressure control solenoid vacuum valve
^ Fuel tank pressure control valve
For functional checks of the components listed above, Refer to EVAP Control System Diagnosis.
Check for any of the following conditions:
^ 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 a DTC P0440 to set.
^ A faulty or erratic fuel tank pressure sensor can cause a DTC P0440 to set.
^ A poor connection at the PCM. Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and a poor terminal to wire connection.
^ A damaged wiring 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.
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 0BD 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 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 vacuum valve. The EVAP tank pressure control solenoid vacuum 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 vacuum 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 vacuum 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. A plugged or leaking EVAP canister surge tank could prevent vacuum from reaching 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.