Circuit Description
The EVAP purge valve allows manifold vacuum to purge the canister. The Powertrain Control Module (PCM) supplies a ground to energize the EVAP purge valve (purge ON). The EVAP purge valve 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 operation is also affected by throttle position.
| • | VIN 1 -- Canister purge will be disabled if TP angle increases to above 33%. Canister purge will be re-enabled when TP angle decreases below 29%. |
| • | VIN K -- Canister purge will be disabled if TP angle increases to above 70%. Canister purge will be re-enabled when TP angle decreases below 66%. |
The EVAP vacuum switch is a normally closed switch positioned in the purge line between the canister and the EVAP purge valve. The EVAP 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 valve ON, DTC P0441 will be set.
Conditions for Setting the DTC
| • | No active TP sensor, IAT sensor, MAP sensor, ECT sensor or MAF sensor DTC(s) set. |
| • | 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 Failure Records data. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn OFF the MIL during the third consecutive trip in which the diagnostic has been run and passed. |
| • | The History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using the scan tool. |
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. |
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.
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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. Refer to Powertrain Control Module Replacement/Programming .
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic System Check performed? | -- | ||||||
2 |
Does EVAP Vacuum Sw. display Purge with the EVAP purge solenoid commanded ON? | -- | ||||||
3 |
Note test result; does scan tool indicate DTC P0441 failed this ign? | -- | Refer to Diagnostic Aids | |||||
4 |
Does the scan tool display Purge? | -- | ||||||
5 | Check the vacuum line to canister for damage or improper connections. Was a problem found? | -- | ||||||
6 |
Does the gauge indicate vacuum greater than the specified value? | 12 in. Hg | ||||||
7 |
Does the scan tool display Purge? | -- | ||||||
8 |
Does gauge indicate vacuum greater than the specified value? | 12 in. Hg | ||||||
9 |
Was a problem found? | -- | ||||||
10 |
Is the test light ON? | -- | ||||||
11 |
Is the test light ON? | -- | ||||||
12 | Check for a poor connection at the PCM. Was a problem found? | -- | ||||||
13 | Check for the following conditions:
Was a problem found? | -- | -- | |||||
14 | Replace the EVAP canister. Refer to Evaporative Emission Canister Replacement . Is action complete? | -- | -- | |||||
15 | Replace the EVAP vacuum switch. Refer to Evaporative Emission Vacuum Switch . Is action complete? | -- | -- | |||||
16 | Locate and repair the cause of no vacuum. Is action complete? | -- | -- | |||||
17 | Check for a poor connection at the EVAP purge solenoid. Was a problem found? | -- | ||||||
18 | Replace the EVAP purge solenoid. Refer to Evaporative Emission Canister Purge Solenoid . Is action complete? | -- | -- | |||||
Replace the PCM. Important: Replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Is action complete? | -- | -- | ||||||
20 |
Note test result; does scan tool indicate DTC P0441 failed this ign? | -- | System OK |
