P0451
System Diagram:
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 ECM (terminal 81)
- 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
- To judge if the fuel tank differential pressure sensor is defective, the ECM
- The ECM
DTC SET CONDITIONS
Test Conditions: Electrical noise
- Throttle valve is closed.
- Vehicle speed is 1.5 km/h (0.93 mph) or less.
Judgment Criteria
- The ECM
- The ECM
NOTE: Rapid voltage occurs due to fuel sloshing during refuelling. However, when the ECM
NOTE: The ECM
- 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.
- Damaged harness in the fuel tank differential pressure sensor circuit.
- ECM
OVERVIEW OF TROUBLESHOOTING
- DTC P0451 can be set if either of the following conditions occur:
1. Faulty fuel differential pressure sensor, related circuit, or ECM
- To check a system blockage, do a performance test which uses a mechanical vacuum gauge and scan tool MB991502 set on the fuel tank differential pressure sensor (TANK PRS SNSR 73.)
The mechanical gauge reading is used to verify scan tool MB991502 reading.
A comparison of the mechanical gauge to scan tool MB991502 determines the problem in the system.
DIAGNOSIS
Required Special Tools:
- MB991502: Scan Tool (MUT-II)
- MB991658: Test Harness Set
STEP 1. 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 the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
1. Connect scan tool MB991502 to the data link connector.
2. Disconnect hose G from the evaporative emission canister side, and plug the hose.
3. Turn the ignition switch to the "ON" position.
4. Set scan tool MB991502 to the data reading mode for item 73, Fuel Tank Differential Pressure Sensor.
- When the fuel cap is removed, the display should be -1.5 to 1.5 kPa.
- When the evaporative emission system pressure pump connect to the fuel filler neck and apply pressure, the display should be increase.
5. Turn the ignition switch to the "LOCK" (OFF) position.
6. Disconnect the evaporative emission system pressure pump, and reinstall the fuel cap.
7. Connect hose G to the canister.
Q: Is the sensor operating properly?
YES: Go to Step 26.
NO: Go to Step 2.
STEP 2. Check the sensor output voltage at intermediate connector D-14 by backprobing.
1. Remove the rear seat cushion. (Refer to Rear Seat.)
2. Pull up the carpet.
3. Disconnect hose G from the evaporative emission canister side, and plug the hose.
4. Turn the ignition switch to the "ON" position.
5. Measure the voltage between terminal 11 and ground by backprobing.
- When the fuel cap is removed, the voltage should be between 2.0 and 3.0 volts.
- When the evaporative emission system pressure pump connect to the fuel filler neck and apply pressure, the display should be increase.
6. Turn the ignition switch to the "LOCK" (OFF) position.
7. Disconnect the evaporative emission system pressure pump, and reinstall the fuel cap.
8. Connect hose G to the canister.
Q: Is the voltage normal?
YES: Go to Step 3.
NO: Go to Step 7.
STEP 3. Check the output circuit voltage at ECM connector C-117
1. Do not disconnect ECM connector C-117
2. Disconnect hose G from the evaporative emission canister side and plug the hose.
3. Turn the ignition switch to the "ON" position.
4. Measure the voltage between terminal 61
- When the fuel cap is removed, the voltage should be between 2.0 and 3.0 volts.
- When the evaporative emission system pressure pump connect to the fuel filler neck and apply pressure, the voltage should be increase.
5. Turn the ignition switch to the "LOCK" (OFF) position.
6. Disconnect the evaporative emission system pressure pump, and reinstall the fuel cap.
7. Connect hose G to the canister.
Q: Is the voltage normal?
YES: Go to Step 4.
NO: Go to Step 6.
STEP 4. Check connectors D-14 at intermediate connector and C-117 at ECM
Q: Are the connectors in good condition?
YES: Go to Step 5.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 26.
STEP 5. 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 the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
1. Connect scan tool MB991502 to the data link connector.
2. Disconnect hose G from the evaporative emission canister side and plug the hose.
3. Turn the ignition switch to the "ON" position.
4. Set scan tool MB991502 to the data reading mode for item 73, Fuel Tank Differential Pressure Sensor.
- When the fuel cap is removed, the display should be -1.5 to 1.5 kPa.
- When the evaporative emission system pressure pump connect to the fuel filler neck and apply pressure, the display should be increase.
5. Turn the ignition switch to the "LOCK" (OFF) position.
6. Disconnect the evaporative emission system pressure pump, and reinstall the fuel cap.
7. Connect hose G to the canister
Q: Is the sensor operating properly?
YES: This malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction. Then go to Step 26.
NO: Replace the ECM
STEP 6. Check connectors D-14, C-127, C-124 at intermediate connector and C-117 at ECM
Q: Are the connectors in good condition?
YES: Repair it because of harness open circuit or damage between fuel tank differential pressure sensor connector D-14 terminal 11 and ECM connector C-117 terminal 61
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 26.
STEP 7. Check the 5-volt supply circuit voltage at intermediate connector D-14 by backprobing.
1. Do not disconnect intermediate connector D-14.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal 9 and ground by backprobing.
- The voltage should be between 4.7 and 5.1 volts.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the voltage normal?
YES: Go to Step 12.
NO: Go to Step 8.
STEP 8. Check the 5-volt supply circuit voltage at ECM connector C-115
1. Do not disconnect ECM connector C-115
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal 81
- The voltage should be between 4.7 and 5.1 volts.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the voltage normal?
YES: Go to Step 9.
NO: Go to Step 10.
STEP 9. Check connectors D-14, C-127, C-124, C-105 at intermediate connector and C-115 at ECM
Q:
YES: Repair it because of harness open circuit or damage between intermediate connector D-14 terminal 9 and ECM connector C-115 terminal 81
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 26.
STEP 10. Check connectors D-14, D-127, C-124, C-105 at intermediate connector and C-115 at ECM
Q: Are the connectors in good condition?
YES: Go to Step 11.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 26.
STEP 11. Check the harness for short circuit to ground between intermediate connector D-14 terminal 9 and ECM connector C-115 terminal 81
Q: Is the harness wire in good condition?
YES: Go to Step 5.
NO: Repair it. Then go to Step 26.
STEP 12. Check the ground voltage at intermediate connector D-14 by backprobing.
1. Do not disconnect connector D-14.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal 10 and ground by backprobing.
- The voltage should be 0.5 volt or less.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the voltage normal?
YES: Go to Step 16.
NO: Go to Step 13.
STEP 13. Check the ground voltage at ECM connector C-115
1. Do not disconnect ECM connector C-115
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal 92
- The voltage should be 0.5 volt or less.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the voltage normal?
YES: Go to Step 14.
NO: Go to Step 15.
STEP 14. Check connectors D-14, C-127, C-124 at intermediate connector and C-115 at ECM
Q: Are the connectors in good condition?
YES: Repair it because of harness open circuit or damage between intermediate connector D-14 terminal 10 and ECM connector C-115 terminal 92
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 26
STEP 15. Check connectors C-115 at ECM
Q: Are the connectors in good condition?
YES: Reinstall the fuel tank. Go to Step 5.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 26
STEP 16. Check the sensor output voltage at fuel tank differential pressure sensor connector D-09.
1. Remove the fuel tank. (Refer to Fuel Tank.)
2. Plug the filler hose, fuel pump feed nipple, return hose, hose L and hose H connected to the fuel tank.
NOTE: If these items are not securely plugged here, the fuel could leak in the next step.
3. Lift the fuel tank.
4. Use special tool (MB991658) to connect terminals 1, 2 and 3 of the fuel tank differential pressure sensor connectors and those of the harness side connector, respectively.
5. Turn the ignition switch to the "ON" position.
6. Measure the voltage between terminal 1 and ground.
- When the plug is disconnected from the filler hose, the voltage should be between 2.0 and 3.0 volts.
- When the evaporative emission system pressure pump connect to the filler hose and apply pressure, the voltage should be increase.
7. Turn the ignition switch to the "LOCK" (OFF) position.
8. Disconnect the evaporative emission system pressure pump.
Q: Is the voltage normal?
YES: Go to Step 17.
NO: Go to Step 19.
STEP 17. Check connector D-09 at fuel tank differential pressure sensor and D-14 at intermediate connector for damage.
Q: Are the connectors in good condition?
YES: Go to Step 18.
NO: Repair or replace it. Refer to Harness Connector Inspection. Reinstall the fuel tank. Refer to Fuel Tank. Then go to Step 26.
STEP 18. Check the harness for short circuit to ground between fuel tank differential pressure sensor connector D-09 terminal 1 and intermediate connector D-14 terminal 11.
Q: Is the harness wire in good condition?
YES: Reinstall the fuel tank. Refer to Fuel Tank. Then go to Step 26.
NO: Repair it, and reinstall the fuel tank. Refer to Fuel Tank. Then go to Step 26
STEP 19. Check the 5-volt supply circuit voltage at fuel tank differential pressure sensor connector D-09.
1. Turn the ignition switch to the "ON" position.
2. Measure the voltage between terminal 3 and ground.
- The voltage should be between 4.7 and 5.1 volts.
3. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the voltage normal?
YES: Go to Step 22.
NO: Go to Step 20.
STEP 20. Check connector D-09 at fuel tank differential pressure sensor and D-14 at intermediate connector for damage.
Q: Are the connectors in good condition?
YES: Go to Step 21.
NO: Repair or replace it. Refer to Harness Connector Inspection. Reinstall the fuel tank. Refer to Fuel Tank. Then go to Step 26.
STEP 21. Check the harness for short circuit to ground between fuel tank differential pressure sensor connector D-09 terminal 3 and intermediate connector D-14 terminal 9.
Q: Is the harness wire in good condition?
YES: Reinstall the fuel tank. Refer to Fuel Tank. Then go to Step 26.
NO: Repair it, and reinstall the fuel tank. Refer to Fuel Tank. Then go to Step 26.
STEP 22. Check voltage at fuel tank differential pressure sensor connector D-09.
1. Turn the ignition switch to the "ON" position.
2. Measure the voltage between terminal 2 and ground.
- The voltage should be 0.5 volt or less.
3. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the voltage normal?
YES: Go to Step 25.
NO: Go to Step 23.
STEP 23. Check connector D-09 at fuel tank differential pressure sensor and D-14 at intermediate connector for damage.
Q: Are the connectors in good condition?
YES: Go to Step 24
NO: Repair or replace it. Refer to Harness Connector Inspection. Reinstall the fuel tank. Refer to Fuel Tank. Then go to Step 26.
STEP 24. Check the harness for short circuit to ground between fuel tank differential pressure sensor connector D-09 terminal 2 and intermediate connector D-14 terminal 10.
Q: Is the harness wire in good condition?
YES: Reinstall the fuel tank. Refer to Fuel Tank. Then go to Step 26.
NO: Repair it, and reinstall the fuel tank. Refer to Fuel Tank. Then go to Step 26
STEP 25. Check connector D-09 at fuel tank differential pressure sensor for damage.
Q: Are the connectors in good condition?
YES: Replace the fuel tank differential pressure sensor, and reinstall the fuel tank. Refer to Fuel Tank. Then go to Step 26.
NO: Repair or replace it. Refer to Harness Connector Inspection. 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.
Q: Is diagnostic trouble code P0451 set?
YES: Go to Step 2.
NO: This diagnosis is complete.