P0451
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)
- 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)
TECHNICAL DESCRIPTION
- To judge if the fuel tank differential pressure sensor is defective, the ECM
- 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
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).
Judgement 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.
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
2. Faulty fuel filler neck evaporative emission ventilation solenoid or blocked vapor line.
- If the fuel filler neck evaporative emission ventilation solenoid is faulty and stays closed or the vapor line is blocked, the pressure inside the fuel tank is increased as the evaporative fuel is not purged especially at hot ambient temperatures. Once the pressure inside the fuel tank reaches 5 kPa (0.073 psi), the sensor output voltage also reaches 4.0 volts. This will set the DTC P0451.
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 Step3.
STEP 3. Check the 5-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-1 6.
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 5.0 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 Step6.
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 27.
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 "ON" 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-210, C-25, C-122
NO: Replace the fuel tank differential pressure sensor. Then go to Step 29.
STEP 10. Check the output circuit voltage at ECM connector C-122
1. Do not disconnect the ECM connector C-122
2. Turn the ignition switch to the "ON" position.
3. Remove the fuel cap.
4. Measure the voltage between terminal 93
- 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-210, C-25, C-122
STEP 11. Check the 5-volt supply circuit voltage at ECM connector C-118
1. Do not disconnect ECM connector C-58
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal 42
- 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-210, C-25, C-118
NO: Go to Step 12.
STEP 12. Check ECM connector C-118
1. Disconnect ECM connector C-118
Q: Is there any failure at ECM connector C-118
YES: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 29.
NO: Go to Step 13.
STEP 13. Check the sensor power supply line for short circuit to ground at ECM connector C-118
1. Disconnect ECM connector C-118
2. Check for the continuity between terminal 42
Q: Does the multi-meter reading exceed the specified value?
YES: Replace ECM or PCM. Then go to Step 29.
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 it necessary. (Refer to Circuit Diagrams - MFI System
STEP 15. Check the ground circuit voltage at ECM connector C-118
1. Do not disconnect ECM connector C-118
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal 49
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-210, C-25, C-118
NO: Go to Step 16.
STEP 16. Check ECM connector C-118
1. Disconnect ECM connector C-118
Q: Is there any failure at ECM connector C-118
YES: Replace ECM or PCM. Then go to Step 27.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 27.
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 27.
NO: Check connectors D-18, D-16 and repair or replace as required. Refer to Harness Connector Inspection. Then go to Step 29.
STEP 18. Check ECM connector C-122
1. Disconnect ECM connector C-122
Q: Is there any failure at ECM connector C-122
YES: Go to Step 29.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 29.
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 29.
NO: Replace the ECM or PCM. Then go to Step 29.
STEP 20. Check for clogging in the evaporator line from hose G to hose I and from hose L to hose P.
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.
3. Turn the pump timer to ON. You can reset the timer as required. (These settings are listed under "Leak Test" in the pump instructions.)
- Air should pass through the hose E.
Q: Does air pass through the air filter?
YES: Go to Step 25.
NO: Go to Step 21.
STEP 21. Check the vent valve module for clogging.
1. Check the orvr vent valve module for clogging.
Q: Air there any clogs?
YES: Replace the vent valve module. Then go to Step 29.
NO: Go to Step 22.
STEP 22. Check for clogging in the evaporator lines I, Q and hose R.
1. Apply vacuum with a hand vacuum pump connected to hose I, Q and hose R.
Q: Are there any clogs?
YES: Replace that hose. Then go to Step 29.
NO: Go to Step 23.
STEP 23. 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 29.
NO: Go to Step 24.
STEP 24. 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 27.
NO: Replace the evaporative emission canister, reinstall the fuel tank. Then go to Step 29.
STEP 25. Check for clogging in the evaporator lines from hose L to hose O.
1. Apply vacuum with a hand vacuum pump connected to from hose L to hose O.
Q: Are there any clogs?
YES: Replace that hose, reinstall the fuel tank filler neck. Then go to Step 27.
NO: Go to Step 26.
STEP 26. Check the check valve A.
1. Only when you blow the check valve from the direction shown, it should pass air.
2. When you blow the check valve, on air should leak from the check valve body.
Q: Is there any failure?
YES: Replace it, and go Step 29.
NO: Go to Step 27.
STEP 27. Check the check valve B.
1. When you blow the check valve from the arrow direction shown above, it should pass more air.
2. When you blow the check valve from the arrow direction shown below, it should pass less air.
3. When you blow the check valve, on air should leak from the check valve body.
Q: Is there any failure?
YES: Replace it, and go to Step 29.
NO: Go to Step 28.
STEP 28. Check for clogging in the evaporator line from hose P.
1. Remove the fuel tank.
2. Carry out the clogging test with a hand vacuum pump on each hose from hose P.
Q: Are there any clogs?
YES: Replace that hose, reinstall the fuel tank. Then go to Step 29.
NO: Reinstall the fuel tank, then go to Step 29.
STEP 29. 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 P0451 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.