Circuit Description
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 purge solenoid
is used to control the flow of fuel vapors from the EVAP canister to the intake manifold.
The EVAP purge solenoid is commanded On (PWM) whenever the EVAP system is in purge
mode. Fuel vapors can be purged at anytime the PCM is in closed loop and the vehicle
is not in a decel. The PCM controls the EVAP purge solenoid by controlling an internal
driver that pulls the solenoid circuit to ground. The EVAP purge solenoid circuit
is monitored for low and high voltage faults. During one part of the EVAP diagnostic
system test, the PCM will close the EVAP purge solenoid and EVAP vent solenoid. DTC P1441
sets when the fuel tank pressure sensor indicates that the pressure is lower than
atmospheric (vacuum) indicating the EVAP purge solenoid is stuck open.
Conditions for Setting the DTC
DTC P1441 will set if fuel tank pressure sensor voltage is indicating
less than 2.00 volts (continuous purge flow) during the EVAP diagnostic system
test when:
| • | Condition exists for 75 seconds |
| • | EVAP vent solenoid is commanded On (closed) |
| • | EVAP purge solenoid is commanded Off (closed) |
| • | Fuel level is between 15 and 85% |
| • | Baro is greater than 75 kPa |
| • | ECT and IAT and at engine startup are between 4°C and 30°C (39°F
and 86°F) |
| • | ECT and IAT are within 8°C (46°F) of each other |
| • | Vehicle speed is less than 113 km/h (70 mph) |
| • | TP angle is between 7 and 35% |
| • | No ECT, fuel tank pressure, IAT, MAP, O2S-1, PCM internal fault, TP or
VSS DTCs have been set |
DTC P1441 diagnostic runs once per ignition cycle (usually for 30 seconds
if no faults exist) during the EVAP diagnostic system test.
P1441 is a (type A) DTC
Diagnostic Aids
Important: If DTC P1640 is set, diagnose that DTC first. A diagnosed EVAP purge
solenoid or EVAP vent solenoid circuit fault may have caused this DTC
to set.
Important: The PCM uses the fuel tank pressure sensor to detect the amount of vacuum pulled
on the EVAP system during the leak diagnostic tests. Make sure the fuel pressure sensor
is not skewed by verifying FUEL TANK PRESS. SENSOR on the scan tool is between 2.35
and 2.85 volts with ignition On and fuel cap removed.
The most likely cause of DTC P1441 is a stuck open EVAP purge solenoid.
Use Scan tool to command the EVAP PURGE SOLENOID On (PWM). The solenoid should click
at an even rate. Replace solenoid if solenoid intermittently sticks.
DTC P1441
