P0441

DTC P0441 EVAP System No Flow During Purge:

DTC P0441 EVAP System No Flow During Purge (continued):

EVAP System Circuit:

CIRCUIT DESCRIPTION

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

^ Engine coolant temperature above 25°C (77°F).

^ After the engine has been running about 2 1/2 minutes on a cold start or 30 seconds on a warm start.

^ The vehicle is operating in closed loop fuel control.

Canister purge commanded duty cycle varies according to operating conditions determined by mass air flow, fuel trim, and intake air temperature. Canister purge will be disabled if Throttle Position (TP) angle increases to above 70%. Canister purge will be re-enabled when TP angle decreases below 66%.

The EVAP purge va6uum switch is a normally closed switch position fled in the purge line between the canister and the EVAP purge solenoid. The EVAP purge vacuum switch will open when vacuum increases to greater than 5 inches of water in the purge line. The PCM monitors the EVAP purge vacuum switch signal to determine of the evaporative emission control system is working properly. If the switch is closed (no purge flow) when the PCM is commanding the EVAP purge solenoid ON, DTC P0441 will be set.

CONDITIONS FOR SETTING THE DTC

^ No active TP sensor, Intake Air Temperature (IAT) sensor, MAP sensor, Engine Coolant Temperature (ECT) sensor or MAF sensor DTC(s) set.

^ Barometric Absolute Pressure (BARO) reading is greater than 70 kPa.

^ Engine Coolant Temperature is less than 113°C (235°F).

^ Intake Air Temperature (IAT) sensor indicates an ambient temperature less than 70°C (158°F).

^ The difference between ECT and IAT is less than 10°C (18°F).

^ Engine speed is between 900 and 5000 RPM

^ TP sensor indicates a throttle position between 2.5% and 40%.

^ Canister purge duty cycle is greater than 85%.

^ Canister purge vacuum switch remains closed (12 volts signal at the PCM).

^ Above conditions for longer than 4 seconds.

ACTION TAKEN WHEN THE DTC SETS

^ The PCM will illuminate the Malfunction Indicator Lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed.

^ The PCM will store conditions which were present when the DTC set as Freeze Frame and Fail Records data.

CONDITIONS FOR CLEARING THE MIL/DTC

^ The PCM will turn the MIL OFF during the third consecutive trip in which the diagnostic has been run and passed.

^ The history DTC will clear afier 40 consecutive warm-up cycles have occurred without a malfunction.

^ The DTC can be cleared by using the scan tool Clear Info function or by disconnecting the PCM battery feed.

DIAGNOSTIC AIDS

Check for the following conditions:

^ Poor connection at PCM. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.

^ Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the EVAP vacuum switch display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the display will indicate the location of the fault.

^ Faulty or damaged canister. A faulty canister may intermittently allow charcoal into the EVAP purge solenoid, EVAP vacuum switch, and associated lines, causing a DTC to be set. Refer to EVAP Canister:

Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

TEST DESCRIPTION

Number(s) below refer to the step number(s) on the Diagnostic Table.

19. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.