Inspection Procedure
SYSTEM DIAGRAM
CAUTION
- EVAP system uses very fine vacuum/pressure of 0.5 psi or even less!
- Vacuum gauge may be broken if excessive vacuum is applied.
COMPONENT LOCATION
TECHNICAL DESCRIPTION
The ECM turns on the evaporative emission ventilation solenoid which shuts off the evaporative emission canister outlet port. Then the evaporative emission purge solenoid is driven. As a result, the fuel system will be set into a negative pressure. When the fuel system reaches negative pressure, the evaporative emission purge solenoid is turned "off', and the EVAP system is sealed. As the fuel pressure inside the fuel tank changes, the ECM judges if there is a leak in the fuel system.
DTC SET CONDITION
When monitored
- Engine coolant temperature lower than 45°C when starting the engine and higher than 60°C (140°F) when drive cycle test begins.
- Engine speed is at between 1600 and 3,500 rpm.
- Power steering pressure switch: "OFF".
- Barometric pressure is higher than 76 kPa (11 psi).
- Engine load is at between 20 and 80 percent.
- Intake air temperature is higher than -10°C (14°F).
- The pressure rise when the evaporative emission purge solenoid and evaporative emission ventilation solenoid are closed is less than 490 Pa (0.071 psi).
- The pressure fluctuation width is less than 667 kPa (0.097 psi).
- Monitoring time: 50 - 100 seconds.
- Purge line or vapor line is clogged.
- Fuel tank, purge line or vapor line seal failed (leak)
- Evaporative emission purge solenoid failed.
- Evaporative emission ventilation solenoid failed.
- Fuel tank differential pressure sensor failed.
- Engine coolant temperature sensor failed.
- Intake air temperature sensor failed.
- Power steering pressure switch failed.
- Use of incorrect fuel.
Judgment Criteria
- Internal pressure of the fuel tank has changed more than 981 Pa (0.142 psi) in 20 seconds after the tank and vapor lines were closed.
TROUBLESHOOTING HINTS
The most likely causes for this code to be set are:
- Loose fuel cap
Defective relief valve of the fuel cap
- Fuel filler neck vent valve failed.
OVERVIEW OF TROUBLESHOOTING
- To determine the cause of the DTC P0442, a performance test is needed which uses a mechanical vacuum gauge and the scan tool set on the tank pressure differential sensor (TANK PRS SNSR 73). The mechanical gauge reading is used to verify the scan tool reading. A comparison of the mechanical gauge to the scan tool determines the problem in the system.
- Prior to doing the performance test, several simple inspections are needed to exclude some possibilities of the symptom.
DIAGNOSIS
Required Special Tool:
MB991 502: Scan Tool (MUT-II)
CAUTION: To prevent damage to the scan tool, turn the ignition switch "OFF" before connecting or disconnecting the scan tool (MUT-II).
In this procedure, the scan tool should be used in the metric mode (showing the value in kPa). If not, set the scan tool by selecting the "System Setup" at the main menu.
Required General Tools:
3 Locking pliers
Thick walled tubing for vacuum tests.
STEP 1. Check for other DTCs.
If any other DTCs are set, please check those DTCs first then follow the steps below.
STEP 2. Evaporative Emission System Leak Monitor Test using scan tool (MUT-II)
NOTE This monitor is carried out at an engine speed of 1,600 rpm or more, transaxle is in "N" or "P" position. The engine speed has to be automatically adjusted.
1. Erase the DTCs using scan tool (MUT-II) Ensure that the fuel cap is securely tightened.
2. Select "System test" and Press "YES" key.
3. Select "EVP LEAK MON" and Press "Yes" key.
4. IF "Evap Leak Mon" is selected before starting the engine, "Engine must be running." is displayed. In this case, start the engine and then select "Evap Leak Mon" again.
5. If "Keep the TPS in idle position. during the test." is displayed, the ECM or PCM adjusts engine speed automatically. A manual adjustment for engine speed is not needed.
6. Keep the idling position during the monitor.
NOTE If the engine speed does not reach 2,000 rpm during the monitor test, adjustment of the Speed Adjusting Screw may be needed. Refer for the adjustment procedure.
7. Item "In Progress" is displayed during the monitor. Keep the engine speed and load within the define range. Scan tool MB991 502 shows these items on the screen. Item "In Progress" will be change from "NO" to "YES" by keeping engine conditions.
8. This screen is displayed when the test has been completed without malfunction.
If the reading is "Test Passed", evaporative emission system is working properly at the moment. Please explain to customer that improperly tightened fuel cap can cause to turn MIL on.
No further steps are needed.
9. This message will be displayed when a malfunction has been detected during the test.
If the reading is "Test Failed & DTCs Set" go to STEP 3.
10. This message is displayed when the monitor was discontinued by a certain reason (input vehicle speed, engine speed and engine load was out of the specified range)
Turn off the ignition switch once and start the monitor from the beginning.
NOTE The monitor will not start unless turning off the ignition switch once and restart the engine.
STEP 3. Using scan tool MB991502, check "Fuel tank pressure differential sensor (73)" output:
In this step, the fuel tank pressure differential sensor reading is checked to determine if the fuel tank pressure differential sensor output is within the normal range.
1. Check the MFI data list item: TANK PRS SNSR 73
2. Watch the sensor reading. This value varies depending on the pressure inside the fuel tank.
3. Remove the fuel cap.
NOTE If the fuel cap is not securely tightened, it might have been the cause of a leak in the EVAP system and set the DTC P0442.
4. After you have removed the fuel cap, the pressure sensor reading should be between -0.5 kPa and 0.5 kPa.
- If the reading is between -0.5 kPa and 0.5 kPa, the fuel tank pressure differential sensor circuit is O.K. Therefore, go to step 4.
- If the reading is not between -0.5 kPa and 0.5 kPa, the fuel tank pressure differential sensor is not working properly. Replace the fuel tank pressure differential sensor.
STEP 4. Check for the fuel vent valve plunger and flapper door operation
NOTE When a fuel nozzle is inserted to the filler neck and the flapper door is opened, the fuel vent valve is closed (plunger moves towards the top of the neck). When the fuel cap is closed, the fuel cap pushes the plunger back in, which then opens the vent valve. If the flapper door or plunger does not operate properly, the vent valve stays closed even after the fuel cap is closed. This may block the vapor passage. A defective vent valve plunger may also cause the fuel cap not to seat properly. Either of these conditions can set the DTC P0442.
1. Remove the fuel cap.
2. Push the flapper in to operate the valve.
NOTE When the flapper is pushed in, the plunger of the valve should move towards the top.
3. Reinstall and tighten the fuel cap until you hear 3 clicks.
4. Remove the cap again and check the protrusion of the plunger to verify if it is pushed back.
5. Distance between the tip of vent valve plunger and that of filler neck should be 28 mm or more.
- If the plunger does not return, replace the fuel filler neck and securely tighten the cap.
- If the operation is O.k., reinstall and securely tighten the fuel cap.
STEP 5. Using scan tool MB991502, actuator test item 08: Evaporative Emission Purge Solenoid.
1. Disconnect from the purge solenoid the hose connected to the canister.
2. Connect a hand vacuum pump to the nipple where you disconnected the hose at the previous step.
3. The vacuum should be maintained when you apply vacuum and the vacuum should leaks when the purge solenoid is activated by the actuator test of the scan tool.
- If correct, go to STEP 6.
- If not, refer to DTC P0443 - Evaporative Emission Control System Purge Control Valve Circuit Malfunction.
STEP 6. Using scan tool MB991502, actuator test item 29: Evaporative Emission Ventilation Solenoid.
1. Disconnect from the canister the hose connected to the vent solenoid valve.
2. Connect a hand vacuum pump to the hose that is disconnected at the previous step.
3. The vacuum should leak when you apply vacuum, and the vacuum should be maintained when the vent solenoid is activated by the actuator test of the scan tool.
- If correct, go to STEP 7.
- If not, refer to DTC P0446 - Evaporative Emission Control System vent Control Malfunction.
STEP 7. Check the purge solenoid-to-air intake plenum hose for blockage
1. Disconnect the purge solenoid-to-air intake plenum hose at the purge solenoid side.
2. Connect a hand vacuum pump to the disconnected hose end.
3. Apply vacuum, and check if the vacuum is not maintained.
- If not go to STEP 9.
- If maintained replace the hose or intake plenum. Then go to STEP 8.
STEP 8. Check the purge solenoid-to-air intake plenum hose for vacuum leakage.
1. Plug the purge solenoid-to-air intake plenum hose at the purge solenoid side.
2. Disconnect the purge solenoid-to-air intake plenum hose at the air intake plenum side.
3. Connect a hand vacuum pump to disconnected hose end.
4. Apply vacuum, and check if the vacuum is maintained.
- If maintained, go to STEP 9.
- If not maintained, replace the hose. Then go to STEP 9.
STEP 9. Check the purge control line.
1. Disconnect the purge control valve-to-purge line vacuum line (A part) at the purge line side.
Connect a hand vacuum pump to the disconnected hose, and apply vacuum.
If the vacuum is maintained, remove the vacuum hose and confirm that the line is clogged.
If there is no clogs, go to 2.
If there is clogs, replace the hose. Then go to 2.
If the vacuum is not maintained, replace the hose. Then go to 2.
2. Disconnect the throttle control valve-to-throttle body positive pressure line (B part) at the throttle body side.
Connect a hand vacuum pump to the disconnected hose, and apply vacuum.
If the vacuum is maintained, remove the positive pressure line and confirm that the line is clogged.
If there is no clogs, go to 3.
If there is clogs, replace the hose. Then go to 3.
If the vacuum is not maintained, replace the hose. Then go to 3.
3. Remove the purge control valve-to-canister line (C part), and check the removed hose for leaks and clogs, and confirm that the check valve is clear of foreign material and faces the correct direction.
If not correct, replace the hose or valve. Then go to 4.
If correct, go to 4.
4. Remove the purge control valve-to-air cleaner line (D part), and check the removed hose for leaks and clogs.
If not correct, replace the line. Then go to Step 10.
If correct, go to Step 10.
STEP 10. Performance test:
NOTE Fuel temperature should be lower than 40°C (130°F) when performance test.
In this step, we verify if the EVAP system works properly, or determine which area of the evaporative emission system has a failure.
To achieve the performance test efficiently, we will use a mechanical vacuum gauge (0 - 750 mmH2O range), a scan tool (MUT-II), and the engine to generate vacuum.
NOTE As we use 0 - 750 mmH2O (0.9 psi) range vacuum gauge, the gauge may be broken if excessive vacuum pressure is applied.
Do not apply a vacuum of more than 350 mmH2O (2.9 kPa).
1. Check the check valve (X pant) on the purge line for clogs and its correct direction.
If correct, go to 2.
If not correct, replace or reverse the valve. Then go to 2.
2. Disconnect the line from the purge control valve to the purge line at A and B parts, and plug the nipple at each line end (see the illustration).
3. Install a mechanical vacuum gauge (0 - 750 mmH2O range) between the EVAP purge solenoid valve and the purge hose that comes from the canister.
4. Before starting the performance test, set the vehicle in the following condition.
- Engine coolant temperature: 80 - 95°C (176 - 203°F).
- Lights and all accessories: OFF
- Transmission: Neutral (M/T), Parking (A/T)
5. Select the item TANK PRS SNSR 73 on the scan tool to see the pressure differential sensor output.
6. Run the engine at idle.
7. Using a locking plier, pinch the hose between the purge solenoid and the intake plenum to close the purge flow, as a preparation of the performance test.
8. Using another locking plier, pinch the vent hose between the canister and the vent solenoid. Momentary, remove the locking plier at the purge hose; this will cause the vacuum build up in the EVAP system.
9. The engine vacuum comes from the purge port through the purge solenoid.
NOTE During this operation, purge solenoid may turn off but will resume in operation in about 20 seconds. Operation of the purge solenoid can be checked by needle fluctuation of the mechanical vacuum gauge.
10. Watch the vacuum reading on the mechanical vacuum gauge and the scan tool.
11. When the vacuum reading reaches 350 mmH2O on the mechanical vacuum gauge and -2.9 kPa on the scan tool, pinch the hose between the purge solenoid and the surge tank using another locking plier; this stops the application of vacuum and seals the EVAP system for the leak test.
NOTE If there is a system failure, either or both vacuum readings may not reach to the above specifications. In this case, you do not need to pinch off the purge hose as shown. Refer to the performance test results table below for further steps.
12. After an elapsed time of 20 seconds, check the fuel tank differential pressure reading on the scan tool.
OK: Change in pressure reading is 0.4 kPa or less (holding -2.5 kPa or more vacuum).
Performance test results table:
STEP 11. Vacuum reading on both the mechanical gauge and the scan tool reaches the specifications and satisfy the specifications after 20 seconds:
EVAP system is properly working at the moment. The cause of DTC might have been a loose fuel cap and the customer may have already tightened the cap. Please explain to the customer that the improperly tightened gas fuel can cause to turn MIL on. No further steps are needed.
STEP 12. Vacuum reading on the mechanical gauge reaches 350 mmH2O but the scan tool does not reach -2.9 kPa:
1. If the vacuum reading on the gauge reaches 350 mmH2O but the reading on the scan tool does not reach -2.9 kPa, either a system blockage or a bad pressure differential sensor may be the cause.
2. To determine if there is a blockage in the system, remove the fuel cap.
- If the vacuum reading on the vacuum gauge (at this point 350 mmH2O) remain the same, there is a blockage in the system, and proceed to the STEP 13.
- If the reading drops to about 0 mmH2O, there is no blockage in the EVAP system. Then the fuel tank pressure differential sensor need to be replaced. After replacing the pressure differential sensor, go to STEP 16.
STEP 13. System blockage inspection
1. Disconnect the vapor hose from the fuel tank to the fuel filler neck tube vent valve (Left one of two hoses shown), and check the mechanical vacuum gauge reading. If the vacuum reading drops, a blockage is in the fuel tank or the roll over valve. If the vacuum reading does not drop, then the blockage is in the EVAP system before the point you disconnected the hose.
2. Disconnect one portion of the EVAP system at a time working towards the front of the vehicle until blockage is found (refer to the illustration below for location and sequence).
3. Repair the location of the blockage and go to STEP 16.
STEP 14. Vacuum readings on both the mechanical gauge and the scan tool do not reach the specifications (350 mmH2O and -2.9 kPa):
This condition shows that there is a significant leakage in the system. The inspection procedure for the large system leakage is the same as the small leakage test in STEP 15.
STEP 15. Vacuum readings on both the mechanical gauge and the scan tool reach the specification (350 mmH2O and -2.9 kPa) but do not maintain the vacuum.
This condition shows that there is a slight leakage in the system. Follow the procedure below to locate the source of the leak.
1. The fuel cap relief valve inspection.
a. Remove the fuel cap and install the filler neck adapter in the emission system tester kit in place of the fuel cap.
b. Plug the nipple on the filler neck adapter.
c. Repeat the performance test. If the EVAP system holds the vacuum, then the fuel cap is faulty. Replace the fuel cap, and go to STEP 16.
2. In order to check the purge hoses at the fuel filler neck area.
3. To find the vacuum leakage in the system, clamp off the one section of the EVAP system at a time, starting from vacuum hose that connects the fuel tank to the filler neck vent valve (Refer to the illustration). Repeat the performance test. This will determine if the vacuum leak is either in the fuel tank area or in the rest of the system.
NOTE In this case, as we clamped off the vacuum hose connecting to the fuel tank, the scan tool (MUT-II) reading will not change. Please use the mechanical gauge reading.
- If the EVAP system hold the vacuum leak is in the fuel tank area. To locate the leakage, pressurize the EVAP system to 3.4 kPa (0.49 psi, 14 inH2O) and look for leaky area using the ultrasonic leak detector in the Evaporative Emission System Tester. After repairing the leakage, go to STEP 16.
- If the vacuum leak still exists, the leak is at other than fuel tank area.
4. Clamp off the vacuum hose one component at a time working towards the front of the vehicle. For example, the next step will be the vacuum hose that connects fuel filler neck vent valve to the canister (2 in the illustration below). Repeat the performance test.
5. If the EVAP system holds the vacuum, the vacuum leak is in the fuel filler neck vent valve area. Repeat it until you find the leakage (Refer to the illustration below for locations and sequence). Repair the leakage and go to STEP 16.
STEP 16. Confirmation Test
After you have repaired system failures, repeat the Evaporative Emission System Leak Monitor test (STEP 2.) to make sure that the EVAP system operates correctly.