P0450

System Diagram:

Fuel Tank Diferential 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 ECM (terminal 42) or PCM (terminal 46) . The ground terminal (terminal 2) is grounded with the ECM (terminal 49) or 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 ECM (terminal 93) or PCM (terminal 92) .

TECHNICAL DESCRIPTION
- To judge if the fuel tank differential pressure sensor is defective, the ECM or 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 ECM or 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: Electrical noise
- Idle switch: ON.
- Vehicle speed is 1.5 km/h (0.93 mph) or less.

Test Conditions: Judgment Criteria
- The ECM or 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 ECM or PCM must see this activity during 8 consecutive idling periods from engine starting.

NOTE: Rapid voltage occurs due to fuel slashing during refueling. However, when the ECM or PCM sees the activity mentioned above 8 consecutive times, it judges that an electrical noise is present.

NOTE: The ECM or 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.
- ECM failed .
- PCM failed .
- Blockage of evaporative emission system (causing high pressure.)

OVERVIEW OF TROUBLESHOOTING
- The DTC P0450 can be set if either of the following conditions occur:

1. Faulty fuel differential pressure sensor, related circuit, or ECM or PCM .
2. Faulty fuel filler neck evaporative emission ventilation solenoid or blocked vapor line.

- To check a system blockage, do a performance test which uses a mechanical vacuum gauge and the scan tool MB991502 set on the fuel tank differential pressure sensor (TANK PRS SNSR73.)

The mechanical gauge reading is used to verify the scan tool MB991502 reading.

A comparison of the mechanical gauge to the scan tool MB991502 determines the problem in the system.

DIAGNOSIS

Required Special Tools:
- MB991502: Scan Tool (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 the "ON" position.
3. Remove the fuel cap.
4. 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.

5. Connect an evaporative emission system pressure pump to the fuel filler neck, and apply pressure.
- The scan tool reading should increase.

Q: Is the scan tool reading within the specified value?

YES: Go to Step 20.

NO: Go to Step 2.

STEP 2. Check the output circuit voltage at intermediate connector D-16.
1. Remove the rear seat cushion.
2. Remove the protector.
3. Do not disconnect intermediate connector D-16.
4. Use special tools (MB991658 and MB991709) to connect terminals 5, 6 and 8 between connectors of the intermediate connector, respectively.
5. Turn the ignition switch to the "ON" position.
6. Remove the fuel cap.
7. Measure the voltage between terminal 5 and ground by backprobing.
- Voltage should be between 2.0 and 3.0 volts.

8. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the multi-meter reading within the specified value?

YES: Go to Step 10.

NO: Go to Step 3.

STEP 3. Check the volt supply circuit voltage at intermediate connector D-16.
1. Do not disconnect intermediate connector D-16.
2. Use special tools (MB991658 and MB991709) to connect terminals 5, 6 and 8 between connectors of the intermediate connector, respectively.
3. Turn the ignition switch to the "ON" position.
4. Measure the voltage between terminal 8 and ground by backprobing.
- Voltage should be between 4.8 and 5.2 volts.

5. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the multi-meter reading within the specified value?

YES: Go to Step 4.

NO: Go to Step 11.

STEP 4. Check the ground circuit voltage at intermediate connector D-16.
1. Do not disconnect intermediate connector D-16.
2. Use special tools (MB991658 and MB991709) to connect terminals 5, 6 and 8 between connectors of the intermediate connector, respectively.
3. Turn the ignition switch to the "ON" position.
4. Measure the voltage between terminal 6 and ground by backprobing.
- Voltage should be between 0.5 volts or less.

5. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the multi-meter reading within the specified value?

YES: Go to Step 5.

NO: Go to Step 15.

STEP 5. Check the output circuit voltage at fuel tank differential pressure connector D-18.
1. Remove the center pipe.
2. Remove the fuel band assembly, tilt the fuel tank.
3. Disconnect fuel tank differential pressure sensor connector D-18.
4. Use special tool (MB991658) to connect terminals 1, 2 and 3 of the disconnected sensor connector and those of the harness side connector, respectively.
5. Turn the ignition switch to the "ON" position.
6. Remove the fuel cap.
7. Measure the voltage between terminal 1 and ground by backprobing.
- Voltage should be between 2.0 and 3.0 volts.

8. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the multi-meter reading within the specified value?

YES: Go to Step 17.

NO: Go to Step 6.

STEP 6. Check the 5-volt supply circuit voltage at fuel tank differential pressure sensor connector D-18.
1. Do not disconnect fuel tank differential pressure sensor connector D-18.
2. Use special tool (MB991658) to connect terminals 1, 2 and 3 of the disconnected sensor connector and those of the harness side connector, respectively.
3. Turn the ignition switch to the "ON" position.
4. Measure the voltage between terminal 3 and ground by backprobing.
- Voltage should be between 4.8 and 5.2 volts.

5. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the multi-meter reading within the specified value?

YES: Go to Step 7.

NO: Go to Step 17.

STEP 7. Check the ground circuit voltage at fuel tank differential pressure sensor connector D-18.
1. Disconnect fuel tank differential pressure sensor connector D-18.
2. Use special tool (MB991658) to connect terminals 1, 2 and 3 of the disconnected sensor connector and those of the harness side connector, respectively.
3. Turn the ignition switch to the "ON" position.
4. Measure the voltage between terminal 2 and ground by backprobing.
- Voltage should be between 0.5 volts or less.

5. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the multi-meter reading within the specified value?

YES: Go to Step 8.

NO: Go to Step 17.

STEP 8. Check fuel tank differential pressure sensor connector D-18 for damage.
1. Disconnect fuel tank differential pressure sensor connector D-18.

Q: Is there any failure at fuel tank differential pressure sensor connector D-18?

YES: Go to Step 9.

NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 26.

STEP 9. Check the output voltage at fuel tank differential pressure sensor connector D-18.
1. Disconnect fuel tank differential pressure sensor connector D-18.
2. Use special tool (MB991658) to connect terminals 2 and 3 of the disconnected sensor connector and those of the harness side connector, respectively.
3. Turn the ignition switch to the "NO" position.
4. Remove the fuel cap.
5. Measure the voltage between terminal 1 and ground by backprobing.
- Voltage should be between 2.0 and 3.0 volts.

6. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the multi-meter reading within the specified value?

YES: Check connectors D-16, C-90, C-28, C-62 or C-59 and repair or replace as required. Refer to Harness Connector Inspection. If connectors D-16, C-90, C-28, C-62 or C-59 are in good condition, check the harness between fuel tank differential pressure sensor connector D-18 and ECM connector C-62 or PCM connector C-59 for short circuit to ground, then repair if necessary. Then go to Step 26.

NO: Replace the fuel tank differential pressure sensor. Then go to Step 26.

STEP 10. Check the output circuit voltage at ECM connector C-42 or PCM connector C-59 .
1. Do not disconnect the ECM connector C-62 or PCM connector C-59 .
2. Turn the ignition switch to the "NO" position.
3. Remove the fuel cap.
4. Measure the voltage between terminal 93 or terminal 92 and ground by backprobing.
- Voltage should be between 2.0 and 3.0 volts.

5. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the multi-meter reading within the specified value?

YES: Go to Step 18.

NO: Check connectors D-16, C-90, C-28, C-62 or C-59 and repair or replace as required. Refer to Harness Connector Inspection. If connectors D-16, C-90, C-28, C-62 or C-59 are in good condition, check the harness between intermediate connector D-16 and ECM connector C-62 or PCM connector C-59 for open circuit or damage. Then repair if necessary. Then go to Step 26.

STEP 11. Check the 5-volt supply circuit voltage at ECM connector C-58 or PCM connector C-55 .
1. Do not disconnect ECM connector C-58 or PCM connector C-55 .
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal 42 or terminal 46 and ground by backprobing.
- Voltage should be between 4.8 and 5.2 volts.

4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the multi-meter reading within the specified value?

YES: Check connectors D-16, C-90, C-28, C-58 or C-55 and repair or replace as required. Refer to Harness Connector Inspection. If connectors D-16, C-90, C-28, C-58 or C-55 are in good condition, check the harness between intermediate connector D-16 and ECM connector C-58 or PCM connector C-55 for open circuit or damage. Then repair if necessary. Then go to Step 26.

NO: Go to Step 12.

STEP 12. Check ECM connector C-58 or PCM connector C-55 for damage.
1. Disconnect ECM connector C-58 or PCM connector C-55 .

Q: Is there any failure at ECM connector C-58 or PCM connector C-55 ?

YES: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 26.

NO: Go to Step 13.

STEP 13. Check the sensor power supply line for short circuit to ground at ECM connector C-58 or PCM connector C-55 .
1. Disconnect ECM connector C-58 or PCM connector C-55 and measure at the harness side.
2. Check for the continuity between terminal 42 or terminal 46 and ground.
- There should be 2 ohms or more.

Q: Does the multi-meter reading exceed the specified value?

YES: Replace ECM or PCM. Then go to Step 26.

NO: Go to step 14.

STEP 14. Check the sensor power supply lines.
1. Check all the sensor power supply lines for damage, which flow through the harness ECM connector (terminal 42) or PCM connector (terminal 46) .

Q: Is there any failure in the sensor power supply lines?
When a failure Is found: Repair if necessary. (Refer to Circuit Diagrams - MFI System , . Then go to Step 26.)

STEP 15. Check the ground circuit voltage at ECM connector C-58 or PCM connector C-55 .
1. Do not disconnect ECM connector C-58 or PCM connector C-55 .
2. Turn the ignition switch to the "NO" position.
3. Measure the voltage between terminal 49 or 57 and ground by backprobing.
- Voltage should be 0.5 volts or less.

4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the multi-meter reading below the specified value?

YES: Check connectors D-16, C-90, C-28, C-58 or C-55 and repair or replace as required. Refer to Harness Connector Inspection. If connectors D-16, C-90, C-28, C-58 are in good condition, check the harness between intermediate connector D-16 and ECM connector C-58 or PCM connector C-51 for open circuit or damage. Then repair if necessary. Then go to Step 26.

NO: Go to Step 16.

STEP 16. Check ECM connector C-56 or PCM connector C-55 for damage.
1. Disconnect ECM connector C-58 or PCM connector C-55 .

Q: Is there any failure at ECM connector C-58 or PCM connector C-55 ?

YES: Replace ECM or PCM. Then go to Step 26.

NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 26.

STEP 17. Check the harness between fuel tank differential pressure sensor connector D-18 and intermediate connector D-16 for open circuit or damage.
1. Disconnect fuel tank differential pressure sensor connector D-18 and intermediate connector D-16.

Q: Is there any failure between fuel tank differential pressure sensor connector D-18 and intermediate connector D-16?

YES: Repair it. Then go to Step 26.

NO: Check connectors D-18, D-16 and repair or replace as required. Refer to Harness Connector Inspection. Then go to Step 26.

STEP 18. Check ECM connector C-62 or PCM connector C-59 for damage.
1. Disconnect ECM connector C-62 or PCM connector C-59 .

Q: Is there any failure at ECM connector C-62 or PCM connector C-59 ?

YES: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 26.

NO: Go to Step 19.

STEP 19. Using scan tool MB991502, check data list item 73: Fuel Tank Differential Pressure Sensor.

CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.

1. Connect scan tool MB991502 to the data link connector.
2. Turn the ignition switch to the "ON" position. 3.Remove the fuel cap.
4. 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.

5. Connect an evaporative emission system pressure pump to the fuel filler neck, and apply pressure.
- The scan tool reading should increase.

Q: Is the scan tool reading within the specified value?

YES: Go to Step 26.

NO: Replace the ECM or PCM. Then go to Step 26.

STEP 20. Check for clogging in the evaporator line from hose G to hose I and from hose L to hose R

1. Remove the module bracket mounting bolts, and disconnect hose G from the evaporative emission ventilation solenoid side, and plug the hoses from which the hoses have been disconnected.
2. Install the Evap pressure pump outlet hose to the fuel tank filler neck as described in the pump manufacturer's instructions.

3. On the Evap pressure pump, set the pressure-hold valve to OPEN, and set the vent valve to CLOSED.
4. Turn the pump timer to ON. You can reset the timer as required. (These settings are listed under "Leak Test" in the pump instructions.)
5. When the hose G is unplugged, the air passes through the hose G.

Q: Does air pass through the hose G?

YES: Go to Step 21.

NO: Go to Step 23.

STEP 21. Check the vent valve module for clogging
1. Check the over vent valve module for clogging.

Q: Air there any clogs?

YES: Replace the vent valve module. Then go to Step 26.

NO: Go to Step 22.

STEP 22. Check for clogging in the evaporator line from hose 0 and hose R.
1. Apply vacuum with a hand vacuum pump connected to hose Q and hose R.

Q: Are there any clogs?

YES: Replace that hose. Then go to Step 26.

NO: Go to Step 23.

STEP 23. Check for clogging In the evaporator lines I.
1. Apply vacuum with a hand vacuum pump connected to hose I.

Q: Are there any clogs?

YES: Replace that hose. Then go to Step 26.

NO: Go to Step 24.

STEP 24. Check for clogging in the evaporator line from hose G and hose H.
1. Remove the fuel tank.
2. Carry out the clogging test with a hand vacuum pump on each hose from hose G and hose H.

Q: Are there any clogs?

YES: Replace that hose, reinstall the fuel tank. Then go to Step 26.

NO: Go to Step 25.

STEP 25. 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.

Q: Does the vacuum pump gauge reading fluctuate?

YES: Reinstall the fuel tank. Then go to Step 26.

NO: Replace the evaporative emission canister, reinstall 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 P0450 does not reset.

Q: Are the DTCs reset?

YES: This diagnosis is complete. (If no malfunctions are not found in all steps, an intermittent malfunction is suspected.) Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction.

NO: Replace the ECM or PCM.