Circuit Description
Canister purge is controlled by a solenoid valve that allows manifold vacuum to purge the canister. The Powertrain Control Module (PCM) supplies a ground to energize the 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.
The EVAP purge vacuum switch is a normally closed switch positioned 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, MAF sensor, IAT sensor, MAP sensor, or Output driver DTC(s) set. |
| • | BARO reading is above 70 kPa. |
| • | Engine Coolant Temperature is below 114°C (237°F). |
| • | Intake Air Temperature (IAT) sensor indicates an ambient temperature above 0°C (32°F). |
| • | The difference between ECT and IAT is less than 100°C (212°F). |
| • | Engine speed is between 550 and 5000 RPM |
| • | Canister purge duty cycle is above 85%. |
| • | Canister purge vacuum switch remains closed (12 volts signal at the PCM). |
| • | Above conditions for longer than 4 seconds. |
| • | IAT sensor less than 70°C (158°F) |
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.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to the Powertrain OBD System Check | |||||
2 |
Does the 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 lines to the EVAP canister for damage or improper connections. Refer to Emission Hose Routing Diagram. 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 the 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 |
Is action complete? | -- | -- | |||||
14 | Replace the EVAP canister. Refer to EVAP Canister. Is action complete? | -- | -- | |||||
15 | Replace the EVAP vacuum switch. Go to Refer to EVAP Vacuum Switch. Is action complete? | -- | -- | |||||
16 | Locate and repair the cause of no vacuum. Is action complete? | -- | -- | |||||
17 |
Was a problem found? | -- | ||||||
18 | Replace the EVAP purge solenoid. Refer to EVAP Canister Purge Solenoid. Is action complete? | -- | -- | |||||
Replace the PCM. Important:: The replacement PCM must be programmed. Refer to PCM Replacement/Programming. Is action complete? | -- | -- | ||||||
20 |
Does the scan tool indicate DTC P0441 failed this ign? | -- | System OK |
