P0451
DTC P0451: Fuel tank Differential Pressure Circuit Range/Performance ProblemSystem Diagram:
Fuel Tank Differential Pressure Sensor Circuit (Part 1):
Fuel Tank Differential Pressure Sensor Circuit (Part 2):
CIRCUIT OPERATION
- The ECM (terminal No. 114) supplies a 5 volts reference signal to the fuel tank differential pressure sensor (terminal No. 3). The fuel tank differential pressure sensor (terminal No. 2) is grounded through the ECM (terminal No. 113).
- The fuel tank differential pressure sensor (terminal No. 1) returns a voltage signal to the ECM (terminal No. 112) that is proportional to the pressure in the fuel tank.
TECHNICAL DESCRIPTION
- The ECM monitors the fuel tank differential pressure sensor signal voltage.
- The ECM determines whether the fuel tank differential pressure sensor signal voltage is within normal operating parameters.
DESCRIPTIONS OF MONITOR METHODS
Detect malfunction if change of fuel tank differential pressure sensor output voltage during idling stays large during specified go/stop operations.
MONITOR EXECUTION
Continuous
MONITOR EXECUTION CONDITIONS (OTHER MONITOR AND SENSOR)
Other Monitor (There is no temporary DTC stored in memory for the item monitored below)
- Evaporative emission purge solenoid monitor
- Evaporative emission ventilation solenoid monitor
- Fuel tank temperature sensor monitor
- Fuel level sensor monitor
Sensor (The sensors below are determined to be normal)
- Mass airflow sensor
- Barometric pressure sensor
- Intake air temperature sensor
- Engine coolant temperature sensor
- Accelerator pedal position sensor
DTC SET CONDITIONS
Logic Flow Chart (Monitor Sequence)
Logic Flow Chart (Monitor Sequence):
Check Conditions
- Throttle valve is closed.
- Vehicle speed is 1.5 km/h (0.93 mph) or less.
Judgement Criteria
- If the voltage signal from the fuel tank differential pressure sensor changes by 0.2 volt or more, DTC P0451 will set. The code may also set if a sudden pressure fluctuation occurs twenty times while the engine is idling, and then four consecutive times during normal driving.
NOTE:
- If the number of sudden pressure fluctuations does not reach twenty during any one period of engine idling, or if the ignition switch is turned OFF, the counter will reset to zero.
- The conditions for deviating from idling operation are as follows:
- Vehicle speed is 50 km/h (31 mph) or greater.
FAIL-SAFE AND BACKUP FUNCTION
- None
OBD-II DRIVE CYCLE PATTERN
Refer to MFI Diagnostic Function - OBD-II Drive Cycle - Pattern 15. OBD-II Drive Cycle
TROUBLESHOOTING HINTS (THE MOST LIKELY CAUSES FOR THIS CODE TO BE SET ARE:)
- Fuel tank differential pressure sensor failed.
- Fuel tank differential pressure sensor circuit harness damage, or connector damage.
- ECM failed.
DIAGNOSIS
Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A
STEP 1. Using scan tool MB991958, check data list item 52:Fuel Tank Differential Pressure Sensor.
CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
1. Connect scan tool MB991958 to the data link connector.
2. Plug the disconnected end of hose E.
3. Turn the ignition switch to the "ON" position.
4. Remove the fuel cap.
5. Set scan tool MB991958 to the data reading mode for item 52, Fuel Tank Differential Pressure Sensor.
- Output voltage should be between 1,500 to 3,500 mV.
6. Connect the evaporative emission system pressure pump (Miller number 6872A) to the fuel tank filler tube by using fuel tank adapter (MLR-8382) and pressurize the fuel tank.
- The fuel tank pressure reading should increase.
7. Turn the ignition switch to the "LOCK" (OFF) position. Then disconnect scan tool MB991958.
8. Remove the evaporative emission system pressure pump (Miller number 6872A) and the fuel tank adapter (MLR-8382), and reinstall the fuel cap.
9. Connect hose E to the evaporative emission canister.
Q: Is the sensor operating properly?
YES : It can be assumed that this malfunction is intermittent. Refer to General (Body and Chassis), How to Use Troubleshooting / Inspection Service Points - How to Cope with Intermittent Malfunctions.
NO : Go to Step 2.
STEP 2. Check harness connector D-21 at fuel tank differential pressure sensor for damage.
Q: Is the harness connector in good condition?
YES : Go to Step 3.
NO : Repair or replace it. Refer to General (Electrical), Harness Connector Inspection. Then go to Step 12.
STEP 3. Measure the sensor supply voltage at fuel tank differential pressure sensor connector D-21 by back probing.
1. Do not disconnect the connector D-21.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal No. 3 and ground by back probing.
- Voltage should be between 4.9 and 5.1 volts.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the measured voltage between 4.9 and 5.1 volts?
YES : Go to Step 6.
NO : Go to Step 4.
STEP 4. Check harness connector B-10 at ECM for damage.
Q: Is the harness connector in good condition?
YES : Go to step 5.
NO : Repair or replace it. Refer to General (Electrical), Harness Connector Inspection. Then go to Step 12.
STEP 5. Check for harness damage between fuel tank differential pressure sensor connector D-21 (terminal No. 3) and ECM connector B-10 (terminal No. 114).
NOTE: Check harness after checking intermediate connector C-47. If intermediate connector is damaged, repair or replace it. Refer to General (Electrical), Harness Connector Inspection. Then go to Step 12.
Q: Is the harness wire in good condition?
YES : Go to Step 11.
NO : Repair it. Then go to Step 12.
STEP 6. Measure the ground voltage at fuel tank differential pressure sensor connector D-21 by back probing.
1. Do not disconnect the connector D-21.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal No. 2 and ground by back probing.
- Voltage should be 0.5 volt or less.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the measured voltage 0.5 volt or less?
YES : Go to Step 9.
NO : Go to Step 7.
STEP 7. Check harness connector B-10 at ECM for damage.
Q: Is the harness connector in good condition?
YES : Go to Step 8.
NO : Repair or replace it. Refer to General (Electrical), Harness Connector Inspection. Then go to Step 12.
STEP 8. Check for harness damage between fuel tank differential pressure sensor connector D-21 (terminal No. 2) and ECM connector B-10 (terminal No. 113).
NOTE: Check harness after checking intermediate connector C-47. If intermediate connector is damaged, repair or replace it. Refer to General (Electrical), Harness Connector Inspection. Then go to Step 12.
Q: Is the harness wire in good condition?
YES : Go to Step 11.
NO : Repair it. Then go to Step 12.
STEP 9. Check harness connector B-10 at ECM for damage.
Q: Is the harness connector in good condition?
YES : Go to Step 10.
NO : Repair or replace it. Refer to General (Electrical), Harness Connector Inspection. Then go to Step 12.
STEP 10. Check for harness damage between fuel tank differential pressure sensor connector D-21 (terminal No. 1) and ECM connector B-10 (terminal No. 112).
NOTE: Check harness after checking intermediate connector C-47. If intermediate connector is damaged, repair or replace it. Refer to General (Electrical), Harness Connector Inspection. Then go to Step 12.
Q: Is the harness wire in good condition?
YES : Go to Step 11.
NO : Repair it. Then go to Step 12.
STEP 11. Replace the fuel tank differential pressure sensor.
1. Replace the fuel tank differential pressure sensor.
2. Carry out a test drive with the drive cycle pattern. Refer to MFI Diagnostic Function - OBD-II Drive Cycle - Pattern 15. OBD-II Drive Cycle
3. Check the diagnostic trouble code (DTC).
Q: Is DTC P0451 set?
YES : Replace the ECM. When the ECM is replaced, register the ID code. Refer to Keyless Operation System (KOS), Diagnosis - ID Code Registration Judgment Table [Vehicles with KOS> or Wireless Control Module, Diagnosis - ID Code Registration Judgment Table [Vehicles with WCM>. Then go to Step 12.
NO : The inspection is complete.
STEP 12. Test the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern. Refer to MFI Diagnostic Function - OBD-II Drive Cycle - Pattern 15. OBD-II Drive Cycle
2. Check the diagnostic trouble code (DTC).
Q: Is DTC P0451 set?
YES : Repeat the troubleshooting.
NO : The inspection is complete.