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 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 fuel tank
pressure sensor, EVAP purge solenoid and EVAP vent solenoid circuits. The ECM also
monitors the EVAP system for small and large leaks. During one part of the EVAP diagnostic
system test the ECM will close both the EVAP purge solenoid and the EVAP vent solenoid.
DTC P1441 sets when the fuel tank pressure sensor indicates that the pressure is lower
than atmospheric pressure (vacuum) indicating the EVAP purge solenoid is stuck open.
DTC PARAMETERS
DTC P1441 sets when the fuel tank pressure indicates less than 2.0 volts (continuous
purge flow) during the diagnostic system test when:
| • | Condition exists for longer than 40 seconds |
| • | Engine load less than 35 % |
| • | MAP is greater than 40 kPa |
| • | Battery voltage is greater than 11.0 volts |
| • | ECT at engine startup is between 8°C and 75°C (46° and 167°F) |
| • | IAT is between 8°C and 50°C (46° and 122°F) |
| • | Long term fuel cells not cleared (if cleared, engine must run longer than
16 minutes and 45) |
| • | Fuel level between 1.3 and 12.7 gallons (5-48 liters) |
| • | Altitude less than 9842 ft. |
| • | No battery voltage, ECM internal fault, ECT, EGR, EVAP purge control,
EVAP vent control, fuel tank pressure, HO2S, IAC, MAP, misfire, TP or VSS DTCs have
been set. |
DTC P1441 diagnostic is run once (usually for 40 seconds if no faults exist)
during the EVAP diagnostic test once the above conditions have been met.
P1441 is a (type B) DTC
DIAGNOSTIC AIDS
The ECM uses the fuel tank pressure sensor to detect the vacuum decay of the
EVAP vent solenoid diagnostic. Make sure the fuel pressure sensor is not skewed by
verifying FUEL TANK PRESS. SENSOR on Scan tool is between 2.35 and 2.85 volts with
ignition On and fuel cap removed.
Check the following for causes of a EVAP purge solenoid stuck open:
| • | EVAP purge solenoid stuck open |
| • | EVAP purge solenoid circuit 428 intermittently shorted to ground or ECM
intermittently shorted to ground internally on circuit 428. |
Note: If DTC P0455 is set, diagnose it first.
