Circuit Description
Once every drive cycle, the EVAP System run a 25-40 second diagnostic
where it monitors possible leaks, the fuel tank pressure sensor, vent value and canister
purge value. This diagnostic has 5 phases and can set several different codes
depending on which part of the diagnostic fails. If in the first phase, the tank vacuum
decays too rapidly, this code will set. It can also set in the third phase if the
tank pressure falls too slowly when the vent and purge are both opened. This code
indicates that the vent value is either blocked open or closed.
DTC Parameters
DTC P0440 will set when:
| • | Vehicle speed not present |
| • | Fuel System in closed loop |
| • | Battery voltage greater than 11.0 volts |
| • | Engine run time greater than 17 minutes |
| | NOTE: Under some operating conditions, this diagnostic may run before a full
17 minutes have expired. |
| • | Altitude less than 9000 ft. |
| • | Fuel level between 1.85 and 14 gal. |
| • | No TP, ECT, VSS, tank pressure, oxygen sensors, idle control, purge valve,
vent valve, battery voltage, misfire, and EGR codes set. |
P0440 are (type B) DTCs.
Diagnostic Aids
Possible causes:
| • | EVAP vent solenoid stuck closed |
| • | Vent hose allowing atmospheric pressure into EVAP canister |
| • | EVAP vent solenoid circuit 1310 intermittently shorted to ground or ECM
intermittently shorted to ground internally on that circuit. |
