The evaporative system includes the following components:

The EVAP purge solenoid valve allows the manifold vacuum to purge the canister. The Vehicle Control Module (VCM) supplies a ground in order to energize the solenoid valve (purge ON). The EVAP purge solenoid control by the VCM is Pulse Width Modulated (PWM) or turned ON and OFF several times a second. The duty cycle (pulse width) is determined by the engine operating conditions including the load, the throttle position, the coolant temperature, and the ambient temperature. The duty cycle is calculated by the VCM, and the purge solenoid is commanded ON when certain conditions have been met.

The system checks for conditions that cause the EVAP system to purge continuously by commanding the EVAP vent solenoid ON and the EVAP purge solenoid OFF (EVAP vent solenoid CLOSED, EVAP purge PWM 0%). If the fuel tank pressure level increases during the test, a continuous purge flow condition is indicated. The following items can cause this condition:

If any of these conditions are present, a DTC P1441 sets. This DTC is a type B DTC.

The following conditions will set the DTC:

1. No MAP sensor DTCs
2. No TP sensor DTCs
3. No VSS DTCs
4. No HO2S DTCs
5. No ECT DTCs
6. The DTC P0125 not active
7. No IAT sensor DTCs
8. No Fuel Level DTCs
9. The ECT is greater than 3.75°C (38.75°F) but less than 30°C (86°F).
10. The IAT is greater than 3.75°C (38.75°F) but less than 30°C (86°F).
11. Start up ECT is not more than 8.25°C (46.85°F) greater than the start up IAT.
12. Start up IAT is not more than 1.5°C (34.7°F) greater than the start up ECT.
13. The Fuel Level is greater than 10% and 85%.
14. The Baro is greater than 72.5 kPa.
15. The System Voltage is greater than 10 volts but less than 17 volts..
16. During the diagnotic test, the VCM detects a continuous open purge flow condition.

The VCM will turn ON the MIL after 2 consecutive driving cycles with the fault active.

The VCM turns OFF the MIL after 3 consecutive driving trips without a fault condition present. A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (the coolant temperature has risen 22°C (40°F) from the start-up coolant temperature and the engine coolant temperature exceeds 71°C (160°F) during that same ignition cycle) or the scan tool clearing feature has been used.

A poor connection, rubbed through wire insulation, or a wire that is broken inside the insulation may cause an intermittent.

Any circuitry, that is suspected as causing the intermittent complaint, should be thoroughly checked for the following conditions:

Refer to Intermittent Conditions .

The numbers below refer to the step numbers on the diagnostic table.

1. When commanded by the scan tool, the EVAP. Canister purge solenoid valve should make a clicking noise. This verifies if the VCM has control of solenoid valve.

2. The canister purge vacuum switch is normally closed when no vacuum (purge) is present. With the key ON and the engine off, there shouldn't be any vacuum (purge) present in the EVAP System.

3. Determines if the reason the EVAP. Canister purge solenoid valve could not be commanded was the result of a faulty solenoid, faulty wiring or faulty VCM.

4. Determines if the canister purge vacuum switch, wiring or VCM is at fault.

5. The VCM supplies a 5 volt reference to the canister purge vacuum switch on the EVAP solenoid control circuit. This step determines if the wiring or VCM is at fault.

6. If the 5 volt reference was not available to the canister purge vacuum switch and no other DTCs were set, then the connection is faulty or the circuit is open between the sensor and the wiring splice from the 5 volt reference circuit.