P0440
Diagnostic Chart:
The evaporative emission (EVAP) system is used to store fuel vapors as to reduce the amount of unburned fuel from escaping into the atmosphere. The EVAP system consists of the EVAP canister, fuel tank pressure (FTP) sensor, EVAP lines and hoses, EVAP purge solenoid (normally closed), EVAP service port, EVAP vent solenoid (normally open) and fuel tank. The ECM monitors the EVAP system for circuit faults in the EVAP purge solenoid, EVAP vent solenoid and FTP sensor circuits. The ECM also monitors the EVAP system for leaks (between EVAP vent and purge solenoid). When certain conditions have been met, the ECM will perform an EVAP diagnostic test at idle with no vehicle speed, which will require a five consecutive phase (A, B, C, D and E) test. DTC P0440 will set if a vacuum cannot be pulled on the EVAP system during Phase D of the EVAP diagnostic system test indicating a large EVAP system leak or insufficient vacuum to the EVAP purge solenoid.
DTC PARAMETERS
DTC P0440 will set if fuel tank pressure cannot be pulled greater than 2.02 FTP sensor volts (less than -4.88 mmHg (-2.61 in H2O)) during phase D of the EVAP diagnostic system test indicating a large EVAP leak when:
^ Condition exists for 8 seconds or no change is detected for 4 seconds
^ EVAP purge solenoid is commanded to a 12% duty cycle
^ EVAP vent solenoid is commanded On
^ Engine is at idle
^ Vehicle speed = 0 mph
^ Engine load less than 35%
^ Main relay voltage is greater than 10.0 volts
^ ECT at engine startup is between 4°C and 55°C (40° and 131°F)
^ IAT is between 4°C and 60°C (40° and 140°F)
^ Fuel tank pressure must be within -13.5 to 6.75 mmHg (-7.23 to 3.61 in H2O) to enable test
^ Long term fuel trim cells learned (if not learned, engine must run longer than 16 minutes and 45 seconds)
^ Fuel level is between 9.1 and 50.7 L (2.4 and 13.4 gallons)
^ No ECT, EVAP purge solenoid, EVAP vent solenoid, fuel tank pressure, idle speed, HO2S, MAF, system voltage, throttle actuator, TP sensor or vehicle speed DTCs have been set.
The entire EVAP diagnostic test will take about 16 seconds to complete when no errors have been detected. If the P0440 diagnostic fails, the rest of the EVAP diagnostic test is aborted and not run again in the ignition cycle.
If an EVAP diagnostic test is aborted due to changing enable criteria, the ECM will run the entire EVAP diagnostic test up to 10 times per ignition cycle.
P0440 is a type B DTC.
DIAGNOSTIC AIDS
IMPORTANT:
^ If DTC P0440, P0442, P0446 or P0496 is set, EVAP special functions on Scan tool will not be allowed. Clear DTCs before performing these tests.
^ The ECM uses the fuel tank pressure sensor to detect the pressure of fuel vapor in the fuel tank during all parts of the EVAP diagnostic system test. Make sure the fuel tank pressure sensor is not skewed by verifying FTP SENSOR on Scan tool is between 1.40 and 1.60 volts with ignition On, engine Off and fuel cap removed.
Make a visual inspection for a large leak of the EVAP system. Use the EVAP Pressure/Purge Diagnostic Chart and Ultrasonic Leak Detector to locate the large leak. Follow operating instructions in the EVAP system description.
Possible causes of a large EVAP leak:
^ Fuel cap missing, incorrectly installed or leaking
^ EVAP vent solenoid valve stuck open
^ EVAP purge solenoid stuck closed/blocked or lack of manifold vacuum to solenoid
^ EVAP line/hose connections disconnected/leaking
^ Primary or secondary fuel sender O-ring leaking
^ Fuel tank pressure sensor seal leaking
^ EVAP canister blocked between the EVAP canister purge and tank ports (air should flow each way between the purge and tank ports at the EVAP canister)
USE THE EVAP SYSTEM PICTURE, WHICH WILL POINT TO POSSIBLE LEAK AREAS.