P0450
System Digram:
Fuel Tank Differential Pressure Sensor Circuit:
Connectors:
CIRCUIT OPERATION
- A 5-volt voltage is supplied to the power terminal of the fuel tank differential pressure sensor (terminal 3) from the PCM (terminal 46). The ground terminal (terminal 2) is grounded with the PCM (terminal 57).
- 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 PCM (terminal 92).
TECHNICAL DESCRIPTION
- To judge if the fuel tank differential pressure sensor is defective, the PCM monitors the fuel tank differential pressure sensor output voltage.
- There are three different sets (A, B, C) of test conditions and the judgment criteria. Based on these test conditions and judgment criteria, the PCM judges if the fuel tank differential pressure sensor output voltage is normal.
NOTE: In rare cases, this DTC may be also set under some fuel and driving conditions regardless of the fuel pressure sensor output voltage when the fuel system is clogged.
DTC SET CONDITIONS
Test Conditions A:
Fuel tank differential pressure sensor output voltage is less than the upper limit of the predetermined value
- Intake air temperature is higher than 5° C (41° F).
- Engine speed is 1,600 r/min or more.
- Volumetric efficiency is between 25 and 80 percent.
- Vehicle speed is 30 km/h (18.7 mph) or more.
- Evaporative emission purge solenoid is driven at a 100 percent duty when the intake air temperature is between 5 and 45° C (41 - 113° F).
Judgment Criteria A
- The sensor output voltage remains 4.0 V or more for 10 seconds or more.
Test Conditions B:
Fuel tank differential pressure sensor output voltage is more than the lower limit of the predetermined value
- Intake air temperature is higher than 5° C (41° F).
- Engine speed is 1,600 r/min or more.
- Volumetric efficiency is between 25 and 80 percent.
- Vehicle speed is 30 km/h (18.7 mph) or more.
- Evaporative emission purge solenoid is not driven when the intake air temperature is 5°C (41°F) or more.
Judgment Criteria B
- The sensor output voltage remains less than 1.0 V for 10 seconds or more.
Test Conditions C:
Electrical noise
- Closed throttle position switch: "ON" <3.0L Engine>
- The throttle valve is closed. <3.5L Engine>
- Vehicle speed is 1.5 km/h (0.93 mph) or less.
Judgment Criteria C
- The PCM looks for rapid voltage changes (electrical noise) equal to 20 or more spikes of 0.2 volts or more in 25 millisecond averaged blocks.
- The PCM must see this activity during 8 consecutive idling periods from engine starting.
NOTE: Rapid voltage occurs due to fuel sloshing during refueling. However when the PCM sees the activity mentioned above 8 consecutive times, it judges that an electrical noise is present.
The PCM determines that the engine is not idling if all of the following conditions are met.
- Engine speed is higher than 2,500 r/min.
- Vehicle speed is 15 km/h (9.3 mph) or more.
- Volumetric efficiency is 55 percent or more.
TROUBLESHOOTING HINTS
The most likely causes for this code to be set are:
- Fuel tank differential pressure sensor failed.
- Open or shorted fuel tank differential pressure sensor circuit, or loose connector.
- PCM failed.
- Blockage of evaporative emission system (causing high pressure)
DIAGNOSIS
Required Special Tools:
MB991502: Scan Toot (MUT-II)
MB991658: Test Harness Set
CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
STEP 1. Using scan tool MB991502, check data list item 73: Fuel Tank Differential Pressure Sensor.
1. Connect scan tool MB991502 to the data link connector.
2. Turn the ignition switch to "ON" position.
3. Remove the fuel cap.
4. Disconnect the hose H from the evaporative emission ventilation solenoid side, and plug.
5. Set scan tool MB991502 to the data reading mode for item 73, Fuel Tank Differential Pressure Sensor.
- The fuel tank pressures should be -1.5 to 1.5 kPa.
6. Connect an evaporative emission system pressure pump to the fuel filler neck, and apply pressure.
- The scan tool reading should increase. If within specifications, go to Step 16.
If not within specifications, go to Step 2.
STEP 2. Check the output circuit voltage at Intermediate connector E-4.
1. Remove the passenger side front seat.
(Refer to Front Seat.)
2. Remove the front scuff plate, and pull up the carpet.
(Refer to Trims.)
3. Do not disconnect Intermediate connector E-44.
4. Turn the ignition switch to "ON" position.
5. Remove the fuel cap.
6. Measure the voltage between terminal 5 and ground by backprobing.
- Voltage should be between 2.0 and 3.0 volts.
7. Turn the ignition switch to "LOCK" (OFF) position.
If within specifications, go to Step 10.
If not within specifications, go to Step 3.
STEP 3. Check the 5-volt supply circuit voltage at Intermediate connector E-44.
1. Do not disconnect Intermediate connector E-44.
2. Turn the ignition switch to "ON" position.
3. Measure the voltage between terminal 17 and ground by backprobing.
- Voltage should be between 4.8 and 5.2 volts.
4. Turn the ignition switch to "LOCK" (OFF) position.
If within specifications, go to Step 4.
If not within specifications, go to Step 11.
STEP 4. Check the ground circuit voltage at Intermediate connector E44.
1. Do not disconnect Intermediate connector E-44.
2. Turn the ignition switch to "ON" position.
3. Measure the voltage between terminal 18 and ground by backprobing.
- Voltage should be 0.5 volt or less.
4. Turn the ignition switch to "LOCK" (OFF) position.
If 0.5 volt or less, go to Step 5.
If more than 0.5 volt, go to Step 15.
STEP 5. Check the output circuit voltage at fuel tank differential pressure connector E-28.
1. Remove the fuel tank.
(Refer to Fuel Tank.)
2. Remove the fuel tank differential pressure sensor from the fuel tank, and connect the fuel tank differential pressure sensor to the harness connector.
3. Turn the ignition switch to "ON" position.
4. Measure the voltage between terminal 1 and ground by backprobing.
- Voltage should be between 2.0 and 3.0 volts.
5. Turn the ignition switch to "LOCK" (OFF) position.
If within specifications, go to Step 10.
If not within specifications, go to Step 6.
STEP 6. Check the 5-volt supply circuit voltage at fuel tank differential pressure sensor connector E-28.
1. Do not disconnect fuel tank differential pressure sensor connector E-28.
2. Turn the ignition switch to "ON" position.
3. Measure the voltage between terminal 3 and ground by backprobing.
- Voltage should be between 4.8 and 5.2 volts.
4. Turn the ignition switch to "LOCK" (OFF) position. If within specifications, go to Step 7.
If not within specifications, go to Step 11.
STEP 7. Check the ground circuit voltage at fuel tank differential pressure sensor connector E-28.
1. Do not disconnect fuel tank differential pressure sensor connector E-28.
2. Turn the ignition switch to "ON" position.
3. Measure the voltage between terminal 2 and ground by backprobing.
- Voltage should be 0.5 volt or less.
4. Turn the ignition switch to "LOCK" (OFF) position.
If 0.5 volt or less, go to Step 8.
If more than 0.5 volt, go to Step 15.
STEP 8. Check fuel tank differential pressure sensor connector E-28 for damage.
If fuel tank differential pressure sensor connector E-28 is in good condition, go to Step 9.
If fuel tank differential pressure sensor connector E-28 is damaged, repair or replace it.
Refer to vehicle level Testing and Inspection.
Then go to Step 26.
STEP 9. Check the output voltage at fuel tank differential pressure sensor connector E-28.
1. Disconnect the fuel tank differential pressure sensor connector E-28.
2. Use special tool (MB991658) to connect terminals 2 and 3 of the harness side connector to those of the sensor side connector, respectively.
3. Turn the ignition switch to "ON" position.
4. Remove the fuel cap.
5. Measure the voltage between sensor side connector terminal 1 and ground.
- Voltage should be between 2.0 and 3.0 volts.
6. Turn the ignition switch to "LOCK" (OFF) position.
If within specifications, check connectors E-44, C-16, C-71, C-90 and repair or replace as required.
Refer to vehicle level Testing and Inspection.
If connectors E-44, C-16, C-71, C-90 are in good condition, check the harness between fuel tank pressure sensor connector E-28 and PCM connector C-90 for short circuit to ground, and then repair if necessary.
Then go to Step 26.
If not within specifications, replace the fuel tank differential pressure sensor. Then go to Step 26.
STEP 10. Check the output circuit voltage at PCM connector C-91
1. Do not disconnect the PCM connector C-91.
2. Turn the ignition switch to "ON" position.
3. Remove the fuel cap.
4. Measure the voltage between terminal 92 and ground by backprobing.
- Voltage should be between 2.0 and 3.0 volt.
5. Turn the ignition switch to "LOCK" (OFF) position.
If within specifications, go to Step 17.
If not within specifications, check connectors E-28, E-44, C-16, C-91 and repair or replace as required.
Refer to vehicle level Testing and Inspection.
If connectors E-28, E-44, C-16, C-91 are in good condition, check the harness between Intermediate connector E-28 and PCM connector C-91 for open circuit or damage. Then repair if necessary.
Then go to Step 26.
STEP 11. Check the 5-volt supply circuit voltage at PCM connector C-90.
1. Do not disconnect PCM connector C-90.
2. Turn the ignition switch to "ON" position.
3. Measure the voltage between terminal 46 and ground by backprobing.
- Voltage should be between 4.8 and 5.2 volts.
4. Turn the ignition switch to "LOCK" (OFF) position.
If within specifications, check connectors E-28, E-44, C-16, C-90 and repair or replace as required.
Refer to vehicle level Testing and Inspection.
If connectors E-28, E-44, C-16, C-90 are in good condition, check the harness between Intermediate connector E-28 and PCM connector C-90 for open circuit or damage. Then repair if necessary.
STEP 12. Check PCM connector C-90 for damage.
If connector C-90 is in good condition, go to Step 13.
If connector C-90 is damaged, repair or replace it.
Refer to vehicle level Testing and Inspection.
Then go to Step 26.
STEP 13. Check the sensor power supply line for short circuit to ground at PCM connector C-90.
1. Disconnect PCM connector C-90 and measure at the harness side.
2. Check for the continuity between terminal 46 and ground.
- There should be 2 ohms or more.
If 2 ohms or more, replace PCM. Then go to Step 26.
If less than 2 ohms, go to Step 14.
STEP 14. Check the sensor power supply lines.
Check all the sensor power supply lines, which flow through the harness PCM connector (terminal 46) and then repair if necessary. (Refer to Circuit Diagrams). Then go to Step 15.
STEP 15. Check the ground circuit voltage at PCM connector C-90.
1. Do not disconnect PCM connector C-90.
2. Turn the ignition switch to "ON" position.
3 Measure the voltage between terminal 57 and ground by backprobing.
- Voltage should be 0.5 volt or less.
4. Turn the ignition switch to "LOCK" (OFF) position.
If 0.5 volt or less, check connectors E-28, E-44, C-16, C-71, C-90 and repair or replace as required.
Refer to vehicle level Testing and Inspection.
If connectors E-28, E-44, C-16 6, C-71, C-90 are in good condition, check the harness between Intermediate connector E-28 and PCM connector C-90 for open circuit or damage, and then repair if necessary.
Then go to Step 26.
If more than 0.5 volt, go to Step 16.
STEP 16. Check PCM connector C-90 for damage.
If connector C-90 is in good condition, replace the PCM.
Then go to Step 17.
If connector C-90 is damaged, repair or replace it.
Refer to vehicle level Testing and Inspection.
Then go to Step 26.
STEP 17. Check PCM connector C-91 for damage.
If connector C-91 is in good condition, go to Step 18.
If connector C-91 is damaged repair or replace it.
Refer to vehicle level Testing and Inspection.
Then go to step 26.
CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to "LOCK" (OFF) position before connecting or disconnecting scan tool M6991502.
STEP 18. Using scan tool MB991502, check data list item 73: Fuel Tank Differential Pressure Sensor.
1. Connect scan tool MB991502 to the data link connector.
2. Turn the ignition switch to "ON" position.
3. Remove the fuel cap.
4. Disconnect the hose H from the evaporative emission ventilation solenoid side, and plug.
5. Set scan tool MB991502 to the data reading mode for item 73, Fuel Tank Differential Pressure Sensor.
- The fuel tank pressure should be -1.5 to 1.5 kPa.
6. Connect an evaporative emission system pressure pump to the fuel filler neck, and apply pressure.
- The scan tool reading should increase.
If within specifications, go to Step 26.
If not within specifications, replace the PCM.
Then go to Step 26.
STEP 19. Check the fuel overflow limiter valve plunger and flapper door operation.
NOTE: The fuel overflow limiter valve plunger opens and closes in sequence with the flapper door and fuel overflow limiter valve plunger.
When the fuel gun is inserted in the fuel filler neck and the flapper door is opened, the fuel overflow limiter valve plunger will close. (The fuel overflow limiter valve plunger will move to the top of the neck.)
When the fuel cap is closed, the fuel cap pushes the fuel overflow limiter valve plunger and the fuel overflow limiter valve plunger opens.
If the flapper door or fuel overflow limiter valve plunger does not operate correctly, the fuel overflow limiter valve plunger will remain closed even if the fuel cap is closed (same state as when the evaporator line is clogged).
This can cause DTC P0450 to occur.
1. Remove the fuel cap.
2. Push the flapper with an ornament remover, etc., to activate the valve.
NOTE: The fuel overflow limiter valve plunger moves upward when the flapper is pushed.
3. Tighten the fuel cap until three clicks are heard.
4. Remove the fuel cap again, and with the fuel overflow limiter valve plunger pushed in, measure the projection amount.
5. Confirm that the distance from the end of the fuel tank filler neck to the end of the fuel overflow limiter valve plunger is 28 mm (1.1 inches) or more.
If the fuel overflow limiter valve plunger does not return completely [when less than 28 mm (1.1 inches)], replace the fuel tank filler neck, completely tighten the fuel cap and go to Step 26.
If the fuel overflow limiter valve plunger has completely returned [when 28 mm (1.1 inches) or more], completely tighten the fuel cap and go to Step 20.
STEP 20. Check for clogging in the evaporator line from hose D to F and from J to L
1. Install the EVAP pressure pump outlet hose to the fuel tank filler neck as described in the pump manufacturer's instructions.
2. On the EVAP pressure pump, set the pressure/hold valve to OPEN, and set the vent valve to CLOSED. Turn the pump timer to ON. You can reset the timer as required. These settings are listed under Leak Test" in the pump instructions.)
3. Air should pass through the air filter.
If the air passes, go to Step 26.
If the air does not pass, go to Step 21.
STEP 21. Check for clogging air filter.
Check the air filter for clogging.
If the air filter is clogged, replace the air filter. Then go to Step 26.
If the air filter is not clogged, go to Step 23.
STEP 22. Check for clogging in the evaporator line from hose F to hose H and hose M, N.
The clogging test with a hand vacuum pump on each hose from hose F to hose H and hose M, N.
If the clogging section is pinpointed, replace that hose, and go to Step 26.
If the location of the leak cannot be pinpointed, go to Step 23.
STEP 23. Check for clogging in the evaporative emission canister.
1. Connect a hand vacuum pump to the vent nipple of the evaporative emission canister.
2. Plug the other two nipples or loop a hose between the other nipples.
3. Apply vacuum. When each nipple is unplugged, the vacuum should fluctuate.
If the applied vacuum fluctuates, and install the fuel tank. Then go to Step 26.
If the vacuum does not fluctuate, replace the evaporative emission canister, install the fuel tank. Then go to Step 26.
STEP 24. Check the evaporative emission ventilation solenoid using the scan tool MB991502. (Actuator test item 29)
1. Turn the ignition switch to "ON" position, and disconnect the hose H from the evaporative emission ventilation solenoid side.
2. Connect the hand vacuum pump to the nipple of the evaporative emission ventilation solenoid from which the hoses have been disconnected.
3. Drive the evaporative emission ventilation solenoid with the scan tool MB991502 actuator test, and confirm that the vacuum does not fluctuate when the vacuum is applied with the hand vacuum pump.
If the evaporative emission ventilation solenoid operates correctly and the applied vacuum does not fluctuate, go to Step 25.
If the evaporative emission ventilation solenoid operates correctly, but the vacuum is not maintained, replace the evaporative emission ventilation solenoid, and then go to Step 26.
If the evaporative emission ventilation solenoid does not operate, refer to the evaporative emission ventilation solenoid trouble code DTC P0446.
STEP 25. Check for clogging in the evaporator line hose
1. Remove the fuel tank.
2. Carry out the clogging test with a hand vacuum pump on each hose I.
If the location of the leak or clog is pinpointed, replace that hose, reinstall the fuel tank, and go to Step 26.
If the location of the leak or clog cannot be pinpointed, and install the fuel tank. Then go to Step 26.
STEP 26. Test the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern.
(Refer to Procedure 1 - Evaporative Emission Control system Leak Monitor.)
2. Read the diagnostic trouble code, and confirm that diagnostic trouble code P0450 does not reset.