Inspection
SYSTEM DIAGRAM
CONNECTORS
CIRCUIT OPERATION
- A 5-volt voltage is supplied to the power terminal of the fuel tank differential pressure sensor (terminal 3) from the ECM (terminal 81). The ground terminal (terminal 2) is grounded with the ECM (terminal 92).
- A voltage proportional to the pressure in the fuel tank is sent from the output terminal of the fuel tank differential pressure sensor (terminal 1) to the ECM (terminal 61).
TECHNICAL DESCRIPTION
- The fuel tank differential pressure sensor outputs the voltage in proportion to the pressure in the fuel tank (differential pressure against the barometric pressure).
- The ECM checks whether the output voltage of the fuel tank differential pressure sensor is within the specified range.
DTC SET CONDITIONS
When monitored
- Engine speed is higher than 1,500 rpm.
- Engine load is between 25 and 80 percent.
Judgment Criteria
- The sensor output voltage is more than 4.5 volts for 10 seconds even if the evaporative emission purge solenoid is driven at a 100 percent duty when the intake air temperature is between 5 and 40°C (41 - 113°F).
or
- The sensor output voltage is less than 0.5 volt for 10 seconds even if the evaporative emission purge solenoid is not driven when the intake air temperature is 5°C (41°F).
When monitored
- A pressure fluctuation of more than 0.2 volt occurs more than 20 times.
Closed throttle position switch: "ON".
Judgment Criteria
- A pressure fluctuation (more than 0.2 volt) occurs more than 20 times per during 15.
- Continuous idling duration.
TROUBLESHOOTING HINTS
The most likely causes for this code to be set are:
- faulty fuel filler neck vent valve.
- Blocked fuel vapor lines.
- Fuel tank differential pressure sensor failed.
- Open or shorted fuel tank differential pressure sensor circuit, or loose connector.
- ECM failed.
OVERVIEW OF TROUBLESHOOTING
- The DTC P0450 can be set if either of the following conditions occur:
1. Faulty fuel tank pressure differential sensor, related circuit, or ECM.
2. Faulty fuel filler neck vent valve or blocked vapor line.
- If the fuel filler neck vent valve is faulty and stays closed or vapor line is blocked, the pressure inside the fuel tank is increased as the evaporative fuel is not purged especially at the hot ambient temperature. Once the pressure inside the fuel tank reaches 6 kPa, the sensor output voltage also reaches and remains 4.5 volts. This will set the DTC P0450.
- To check a system blockage, a performance test is needed which uses a mechanical vacuum gauge and the scan tool (MUT-II) 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.
DIAGNOSIS
Required Special Tool:
MB991502: 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.
Scan tool by selecting the "System Setup" at the main menu.
STEP 1. 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 is operating correctly.
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.
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 DTC could be caused by an intermittent electrical malfunction, or by a blockage in the EVAP system. Go to step 2.
If the reading is not between -0.5 kPa and 0.5 kPa, there is an electrical malfunction. Go to step 10.
STEP 2. Check 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 and set the DTC P0450.
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 the fuel cap until you hear 3 click sounds.
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 3. 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, transaxles 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 4.
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 4. 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 5.
- If maintained, replace the hose or intake plenum. Then go to STEP 6.
STEP 5. 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 6.
- If not maintained, replace the hose Then go to STEP 6.
STEP 6. 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 7.
If correct, go to Step 7.
STEP 7. 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 part) 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.
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.
9. Watch the vacuum reading on the mechanical vacuum gauge and the scan tool.
10. 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.
11. 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 8. 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. It can be assumed that this malfunction is intermittent electrical wiring problem. Refer to "How to Cope with Intermittent Malfunctions".
STEP 9. Vacuum reading or 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 reading drops to about 0 mmH2O, there is no blockage in the EVAP system. Then the fuel tank pressure differential sensor need to be tested. Go to pressure differential sensor need to be tested. Go to STEP 10 Tank Pressure Differential Sensor Inspection.
- 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 11.
STEP 10. Tank Pressure Differential Sensor Inspection:
Caution: In removing the tank pressure differential sensor from fuel tank, take precautions, because the fuel in fuel tank might brime over.
1. Remove the rear seat cushion and protector.
2. Remove the tank pressure differential sensor. Do not disconnect the connector at this point.
3. Connect the tank pressure differential sensor to a hand vacuum pump and mechanical vacuum gauge (0 - 750 mmH2O range).
4. Turn the ignition switch "ON".
5. Using scan tool check data list item 73: TANK PRESS SNSR while applying vacuum.
6. If correct, go to STEP14. If not, replace the tank pressure differential sensor and then go to STEP 18.
STEP 11. System blockage inspection
1. Disconnect the vapor hose from the fuel tank to the fuel filler neck tube vent valve, 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 13.
STEP 12. 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 13.
STEP 13. 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 18.
2. In order to check the purge hose at the fuel filler neck area, remove the filler neck protector at the left rear wheel house.
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 18.
- 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 18.
STEP 14. Check the circuits at the fuel tank differential pressure sensor connector E-58.
1. Disconnect the connector E-58 and check the physical condition of the connector. Look for loose pins or corrosion.
2. Turn the ignition switch "ON".
3. Measure at the harness side voltage between terminal 3 and ground.
- Voltage should be between 4.8 and 5.2 volts.
4. Turn the ignition switch "OFF".
5. Check for continuity between terminal 2 and ground.
- There should be continuity (0 Ohm).
If all checks above meet the specifications, the pressure sensor or ECM may be faulty. Then, go to Step 16.
If any check above does not met the specifications, there is a wiring failure between the pressure sensor and ECM or failure in ECM. Go to Step 17.
STEP 15. Check the harness wire between the fuel tank differential pressure sensor connector E-58 (terminal 1) and the ECM connector B-55 (terminal 61).
Check the continuity between the pressure sensor connector E-58 (terminal 1) and the ECM connector B-55 (terminal 61).
- If there is continuity, reinstall all the removed parts and carry out the performance test (STEP 7). If the scan tool reading still does not reach -2.9 kPa, then replace the ECM and go to Step 18.
- If there is no continuity, repair the wiring harness. Then go to Step 18.
STEP 16. Check harness connectors B-55 and B-56 at the ECM for damage.
- If harness connector B-55 and/or 8-56 is damaged, repair or replace them. Refer to Connector Inspection Service Points.
- If harness connector 8-55 and B-56 are in good conditions, then go to Step 17.
STEP 17. Check the harness wire between the fuel tank differential pressure sensor connector E-58 and the ECM connector B-55 and B-56.
Check the continuity between the pressure sensor connector E-58 and the ECM connector B-55 and B-56.
If there is continuity, replace the ECM.
If there is no continuity, repair or replace the wiring harness or connectors. Then go to Step 18.
NOTE Check the wire after checking the intermediate connectors 0-29 and E-60. If the intermediate connectors are faulty, repair or replace them. Refer to Connector Inspection Service Points.
STEP 18. Performance test
1. Connect the purge control valve line.
2. After you have repaired system failures, repeat the Evaporative Emission System Leak Monitor test (STEP 3.) to make sure that the EVAP system operates correctly.