Refer to Engine Controls Schematics
EVAP Controls,and IAC Valve
and to
Fuel Supply System
.
Circuit Description
The powertrain control module (PCM) monitors the positive or negative pressure in the fuel tank using the fuel tank pressure sensor. Under certain engine operating conditions, the PCM turns ON the EVAP pressure switching solenoid in order to control the pressure in the EVAP system. The PCM is able to detect any abnormal conditions by the fluctuation of this pressure. The diagnostics performed by the fuel tank pressure sensor can warn the driver of a malfunction in the EVAP system by illuminating the MIL. The EVAP control system prevents the emission of the fuel vapors. The fuel vapor generated in the fuel tank while driving or idling enters the EVAP canister where a charcoal element absorbs and stores the fuel vapor. The EVAP canister is purged by the PCM controlled EVAP canister purge valve. The EVAP canister purge valve releases the fuel vapors into the intake manifold to be burned in the combustion process.
Conditions for Setting the DTC
The pressure indicated in the EVAP canister does not drop when the EVAP canister purge valve is ON.
OR:
The pressure indicated in the EVAP canister remains very low when compared to atmospheric pressure when the EVAP canister purge solenoid valve is OFF.
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with the fault active. |
| • | The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer. |
Conditions for Clearing the MIL/DTC
| • | The PCM turns OFF the MIL on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present. |
| • | A DTC will clear after 40 consecutive warm-up cycles have occurred without a fault. |
| • | A DTC can be cleared by using the scan tool Clear Information function. |
Diagnostic Aids
| • | If DTC P0441 is the only EVAP DTC set, the most likely cause is an inoperable EVAP canister purge valve. Inspect the EVAP canister purge valve carefully for faulty connections and erratic operation. |
| • | An intermittent DTC P0441 can be caused by a faulty EVAP canister. An EVAP canister that has released carbon particles can cause the EVAP canister purge valve to fail and leak intermittently. Inspect the EVAP purge system for carbon contamination before returning the vehicle to service. Refer to Evaporative Emission System Cleaning . |
| • | A DTC P0441 is more likely to set during city driving. Avoid operating the vehicle on the highway when validating DTC P0441. |
| • | Clear the DTCs. Road test the vehicle while monitoring the EVAP Purge test in the MIL/System Status selection under System Information on the scan tool. When the EVAP Purge test indicates complete with a YES status, check for DTC P0441 under Last Test Failed. If there is no DTC P0441 indicated, the DTC is intermittent and the purge system diagnostic is indicating OK at this time. |
| • | For functional checks of the components listed above, refer to Evaporative Emission Control System Diagnosis . |
| • | An intermittent malfunction may be caused by a fault in any of the EVAP solenoid electrical circuits. Inspect the wiring harness and components for an intermittent condition. Refer to Intermittent Conditions . |
If the DTC cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.
Test Description
The numbers below refer to the step numbers in the diagnostic table.
-
The OBD System Check prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
-
This step checks the EVAP control system components for correct installation or damage. Inspect all lines and hoses. This includes a manufacturer approved gas cap that is correctly installed and tightened.
-
This step checks for the correct function of the EVAP canister purge valve.
-
This step checks the control circuit of the EVAP canister purge valve. Because the control circuit of the EVAP canister purge valve is PWM, the test lamp flickers during illumination, when commanded ON by the scan tool. This is the normal condition, indicating that the PCM and control circuit are OK.
-
This step determines if a fuel tank pressure sensor malfunction is present. The input signal of the fuel tank pressure sensor should indicate atmospheric pressure with the fuel tank filler cap removed. The fuel tank pressure sensor will vary with atmospheric pressure. A typical pressure at sea level is between 0.0-0.99 mm Hg (0.0-0.5 in H2O).
-
This step checks for a possible leak in the EVAP system. The purpose of this inspection is to determine whether 5 to 6 inches of H2O can be obtained and held for at least 2 minutes.
-
This step checks whether there is trapped negative or positive pressure at the FTP sensor.
-
This step checks for leaks in the fuel supply system. By plugging the ORVR vent line and the EVAP vapor line, the fuel tank, the fuel filler hose assembly, and the fuel tank components can be pressurized and checked for leaks. Be sure to check all connections and sealing points for leaks.
-
This step determines if the malfunction that caused the DTC P0441 is still present. Operating the vehicle in Check mode enhances the diagnostic capabilities of the PCM. The EVAP Purge diagnostic can be monitored on the scan tool under the MIL/System Status selection of System Information. When the EVAP Purge test displays a YES status, indicating that the purge system diagnostic is completed, check for DTC P0441 in the Last Test Failed screen of the scan tool. If there is no DTC P0441 displayed the EVAP purge system diagnostic has run and passed, indicating that no malfunction was present this time. The DTCs MUST be cleared in order to view the Current Status of the system diagnostics being performed. Do not forget that the MIL/System Status tests only indicate that the test has run, not whether the test passed or failed. The Last Test Failed screen must be checked for related DTCs in order to determine the outcome of the diagnostic test involved. For additional information on check mode operation refer to Powertrain Control Module Diagnosis.
-
The EVAP canister has component parts that cannot be diagnosed or tested on the vehicle. The EVAP canister should be inspected and tested for correct operation by performing the EVAP canister inspection procedures in EVAP Control System Diagnosis.
Step | Action | Values | Yes | No | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | ||||||||||||||
2 | Install a scan tool and check for DTCs. Is a DTC P0450 present? | -- | Go to Step 3 | |||||||||||||
Refer to the Evaporative Emission Control System Operation Description for EVAP system hose routing diagrams.
Was repair necessary? | -- | Go to Step 48 | Go to Step 4 | |||||||||||||
Air should NOT pass through the solenoid and out the upper port. Did the EVAP canister purge valve pass both tests? | -- | Go to Step 9 | Go to Step 5 | |||||||||||||
5 | Measure the resistance of the EVAP canister purge valve with a digital multimeter (DMM). Is the resistance less than the specified range? | 27-33 ohms at 20°C (68°F) | Go to Step 42 | Go to Step 6 | ||||||||||||
6 |
Does the test lamp illuminate? | -- | Go to Step 7 | Go to Step 8 | ||||||||||||
Did the test lamp illuminate only when the EVAP canister purge valve was commanded ON? | -- | Go to Step 38 | Go to Step 45 | |||||||||||||
8 | Repair the open in the ignition positive voltage circuit of the EVAP canister purge valve. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 48 | -- | ||||||||||||
Is the fuel tank pressure sensor within the specified range? | 0.0-0.99 mm Hg (0.0-0.5 in H2O) | Go to Step 10 | Go to Step 22 | |||||||||||||
10 |
Does the test lamp illuminate? | -- | Go to Step 11 | Go to Step 13 | ||||||||||||
11 |
Air should pass through the solenoid and out the upper port. Did the EVAP canister vent valve pass both tests? | -- | Go to Step 12 | Go to Step 39 | ||||||||||||
12 |
Does the test lamp illuminate? | -- | Go to Step 37 | Go to Step 14 | ||||||||||||
13 | Repair the open in the ignition positive voltage circuit of the EVAP canister vent valve. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 48 | -- | ||||||||||||
14 | Measure the resistance of the EVAP canister vent valve with a DMM. Is the resistance within the specified range? | 25-30 ohms at 20°C (68°F) | Go to Step 15 | Go to Step 39 | ||||||||||||
Does the EVAP system hold the specified pressure for at least 2 minutes? | 8.5-10.5 mm Hg (4.5-5.5 in. H2O) | Go to Step 17 | Go to Step 16 | |||||||||||||
16 |
Was a repair necessary? | -- | Go to Step 48 | Go to Step 30 | ||||||||||||
17 |
Does the test lamp illuminate? | -- | Go to Step 18 | Go to Step 21 | ||||||||||||
18 |
Did the EVAP pressure switching solenoid pass all the tests? | -- | Go to Step 19 | Go to Step 33 | ||||||||||||
19 |
Does the test lamp illuminate? | -- | Go to Step 37 | Go to Step 20 | ||||||||||||
20 | Refer to the Evaporative Emission Control System Operation Description for the EVAP system hose routing diagram used in the following procedure.
Were any EVAP or fuel supply system leaks found? | 56 mm Hg (30 in. H2O) | Go to Step 32 | Go to Step 43 | ||||||||||||
21 | Repair the open in the ignition positive voltage circuit of the EVAP pressure switching solenoid. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 48 | -- | ||||||||||||
Is the fuel tank pressure sensor within the specified range? | 0.0-0.99 mm Hg (0.0-0.5 in H2O) | Go to Step 23 | Go to Step 24 | |||||||||||||
23 |
Is the action complete? | -- | Go to Step 48 | -- | ||||||||||||
24 |
Does the voltage equal the specified value? | 5.0 V | Go to Step 25 | Go to Step 26 | ||||||||||||
25 | Measure the voltage on the harness side of the connector cavity 2 with a DMM. Is the voltage near the specified value? | 4.9 V | Go to Step 28 | Go to Step 27 | ||||||||||||
26 | Repair the open in the reference voltage circuit of the fuel tank pressure sensor between the sensor and SP259. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 48 | -- | ||||||||||||
27 |
Was a repair necessary? | -- | Go to Step 48 | Go to Step 47 | ||||||||||||
28 | Probe the sensor connector cavity 1 on the harness side with a test lamp connected to B+. Does the test lamp illuminate? | -- | Go to Step 36 | Go to Step 29 | ||||||||||||
29 | Repair the open in the ground circuit of the fuel tank pressure sensor between the sensor and S206. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 48 | -- | ||||||||||||
Refer to the Evaporative Emission Control System Operation Description for the EVAP system hose routing diagram used in the following procedure.
Were any EVAP system or fuel supply system leaks found? | 56 mm Hg (30 in. H2O) | Go to Step 32 | Go to Step 31 | |||||||||||||
31 | Replace the EVAP canister. Refer to Evaporative Emission Canister Replacement . Is the action complete? | -- | Go to Step 48 | -- | ||||||||||||
32 | Repair or replace the leaking EVAP system or fuel tank component. Is the action complete? | -- | Go to Step 48 | -- | ||||||||||||
33 | Measure the resistance of the EVAP pressure switching solenoid with a DMM. Is the resistance less than the specified value? | 27 ohms at 20°C (68°F) | Go to Step 34 | Go to Step 35 | ||||||||||||
34 | Replace the EVAP pressure switching solenoid and the PCM. Refer to Evaporative Emission Pressure Switching Solenoid Replacement and to Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 48 | -- | ||||||||||||
35 | Replace the EVAP pressure switching solenoid. Refer to Evaporative Emission Pressure Switching Solenoid Replacement . Is the action complete? | -- | Go to Step 48 | -- | ||||||||||||
36 | Replace the fuel tank pressure sensor. Refer to Fuel Tank Pressure Sensor Replacement . Is the action complete? | -- | Go to Step 48 | -- | ||||||||||||
37 |
Was a repair necessary? | 27 ohms at 20°C (68°F) | Go to Step 48 | Go to Step 47 | ||||||||||||
38 |
Notice: The EVAP canister may have released carbon particles which caused this part to fail and may cause damage to other components. Check the EVAP canister for loose carbon before returning the vehicle to service. Replace the EVAP canister purge valve. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement . Is the action complete? | -- | Go to Step 48 | -- | ||||||||||||
39 | Measure the resistance of EVAP canister vent valve with a DMM. Is the resistance less than the specified range? | 25-30 ohms at 20°C (68°F) | Go to Step 40 | Go to Step 41 | ||||||||||||
40 | Replace the EVAP canister vent valve and the PCM. Refer to Evaporative Emission Canister Vent Solenoid Valve Replacement and Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 48 | -- | ||||||||||||
41 | Replace the EVAP canister vent valve . Refer to Evaporative Emission Canister Vent Solenoid Valve Replacement . Is the action complete? | -- | Go to Step 48 | -- | ||||||||||||
42 | Replace the EVAP canister purge valve and the PCM. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement and Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 48 | -- | ||||||||||||
Did a DTC P0441 set? | -- | Go to Step 44 | Go to Diagnostic Aids | |||||||||||||
Was the EVAP canister replaced? | -- | Go to Step 48 | Go to Step 46 | |||||||||||||
45 |
Was a repair necessary? | -- | Go to Step 48 | Go to Step 47 | ||||||||||||
46 |
Was a wiring fault found and repaired on either solenoid circuit? | -- | Go to Step 48 | Go to Step 47 | ||||||||||||
47 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 48 | -- | ||||||||||||
48 |
Are any DTCs displayed on the scan tool? | -- | System OK |
