The diagnostic strategy for the evaporative emission (EVAP) system uses a vacuum pump to test for system leaks, after the engine is OFF. A unique fuel tank, EVAP canister, and EVAP vacuum leak pump work together to provide enhanced system diagnosis. The vacuum leak pump, the fuel tank pressure (FTP) sensor and the EVAP canister vent valve are all integral parts of one assembly. The assembly is attached directly to the EVAP canister, located near the fuel tank.

After the vehicle has sat with the engine OFF for greater than 5 hours and the engine coolant temperature is less than 35°C (95°F), a comprehensive diagnostic is enabled. The complete diagnostic test can take up to 15 minutes to run, with leak detection comprising the largest portion of the test.

The EVAP canister purge valve is used to purge fuel vapor from the EVAP canister to the intake manifold. Ignition voltage is supplied directly to the EVAP canister purge solenoid valve. The powertrain control module (PCM) controls the solenoid by grounding the control circuit with a solid state device called a driver. The EVAP canister purge valve is pulse width modulated (PWM). The PCM can determine if the EVAP purge solenoid is operating correctly by monitoring the changes in fuel tank pressure.

The following table illustrates the relationship between the ON and OFF states, and the OPEN or CLOSED states of the EVAP canister purge and vent valves.

Condition 1

Condition 2

Condition 1

The pressure indicated in the EVAP canister and the fuel tank does not drop when the EVAP canister purge solenoid is ON.

OR:

The pressure indicated in the EVAP canister remains very low when compared to atmospheric pressure when the EVAP canister purge solenoid is OFF.

Condition 2

The pressure indicated by the fuel tank pressure sensor during EVAP vacuum pump operation is not within the specified values.

DTC P0441 is a Type B DTC.

DTC P0441 is a Type B DTC.

Schematic Reference

Engine Controls Schematics

Description and Operation

Evaporative Emission Control System Description

Connector End View Reference

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

J 23738-A Vacuum Pump

1. Command the EVAP purge solenoid ON and OFF with a scan tool. You should hear the solenoid click when commanded ON and OFF.
2. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

1. Ignition ON, observe the DTC information with a scan tool. Verify that DTC P2420 is not set.

⇒	If the DTC is set, diagnose first. Refer to DTC P2419 or P2420.

2. Ignition OFF, disconnect the harness connector at the EVAP purge solenoid.
3. Ignition ON, verify a test lamp illuminates between the ignition 1 voltage circuit terminal 2 and ground.

⇒	If the test lamp does not illuminate, test the ignition 1 voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition 1 voltage circuit fuse is open, test all components connected to the ignition 1 voltage circuit and replace as necessary.

4. Ignition OFF, connect a test lamp between the control circuit terminal 1 and the ignition 1 voltage circuit terminal 2.
5. Ignition ON, command the EVAP purge solenoid ON and OFF with a scan tool. The test lamp should be pulsing ON and OFF when activated.

⇒	If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the PCM.

⇒	If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If circuit tests normal, replace the PCM.

6. Connect a vacuum gauge to the purge port of the EVAP purge solenoid.
7. Engine running, verify the vacuum gauge reading is zero.

⇒	If the vacuum pressure is greater than the specified range, replace the EVAP purge solenoid valve.

8. Command the EVAP purge solenoid ON with the scan tool. Verify the vacuum gauge reads manifold vacuum when the solenoid is activated.

⇒	If the vacuum pressure is less than the specified range, replace the EVAP purge solenoid valve.

9. If all circuits test normal, test for the following conditions:

•	DTC P0455 was also set--refer to DTC P0455 or P0456

•	A blockage or restriction in the purge line between the purge solenoid and the EVAP canister

•	A faulty EVAP canister--refer to Evaporative Emission Control System Diagnosis

1. Ignition OFF, disconnect the harness connector at the EVAP purge solenoid.
2. Test for 26-30 ohms at 20°C (68°F) between the control terminal 1 and the ignition 1 voltage terminal 2.

⇒	If not within the specified range, replace the EVAP purge solenoid.

3. Test for infinite resistance between each terminal and the EVAP purge solenoid housing.

⇒	If not the specified value, replace the EVAP purge solenoid.

4. Connect the J 28742-A to a vacuum port of the EVAP purge solenoid. Apply 34 kPa (10 inch Hg) of vacuum to the EVAP purge solenoid port. You should be able to obtain and hold vacuum pressure.

⇒	If the vacuum pressure is less than the specified range, replace the EVAP purge solenoid valve.

5. Connect a 10A fused jumper between the EVAP purge solenoid ignition 1 voltage terminal 2 and B+.
6. Connect a second fused jumper between the EVAP purge solenoid ground terminal 1 and ground. The vacuum pressure should decrease to zero when voltage is applied.
7. If vacuum pressure is greater than zero, replace the EVAP purge solenoid valve.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.