P0451
DTC P0451: Evaporative Emission System Pressure Sensor Range/PerformanceSystem Diagram:
Fuel Tank Differential Pressure Sensor Circuit Part 1:
Fuel Tank Differential Pressure Sensor Circuit Part 2:
CIRCUIT OPERATION
- The PCM (terminal 21) supplies a 5-volt reference signal to the fuel tank differential pressure sensor (terminal 3). The fuel tank differential pressure sensor (terminal 2) is grounded through the PCM (terminal 22).
- The fuel tank differential pressure sensor (terminal 1) returns a voltage signal to the PCM (terminal 23) that is proportional to the pressure in the fuel tank.
TECHNICAL DESCRIPTION
- The PCM monitors the fuel tank differential pressure sensor signal voltage.
- The PCM 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
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
Logic Flow Chart:
LOGIC FLOW CHARTS (Monitor Sequence)
DTC SET CONDITIONS Check Conditions
- Throttle valve is closed.
- Vehicle speed is 1.5 km/h (0.93 mph) or less.
Judgment 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.
NOTE: The conditions for deviating from idling operation are as follows:
- Vehicle speed is 50 km/h (31 mph) or greater.
OBD-II DRIVE CYCLE PATTERN
Refer to 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:)
- Malfunction of the fuel tank differential pressure sensor.
- A damaged harness in the fuel tank differential pressure sensor circuit.
- Malfunction of the PCM.
OVERVIEW OF TROUBLESHOOTING
- DTC P0451 can be set by a faulty fuel tank differential pressure sensor or related circuit, or PCM failure.
- To check for system blockage, do a performance test which uses a mechanical vacuum gauge and scan tool MB991958 set on the fuel tank differential pressure sensor (TANK PRS SNSR 73). The mechanical gauge reading is used to verify scan tool MB991958 reading. A comparison of the mechanical gauge with the reading on scan tool MB991958 will locate a problem in the system.
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
- MB991658: Test Harness Set
- MB991923: Power Plant ECU Check Harness
STEP 1. Using scan tool MB991958, check data list item 73: 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. Disconnect hose G from the evaporative emission canister, and plug the hose.
3. Turn the ignition switch to the "ON" position.
4. Remove the fuel cap.
5. Set scan tool MB991958 to the data reading mode.
- Item 73, Fuel Tank Differential Pressure Sensor.
- The fuel tank pressure reading on the scan tool should be -1.5 to 1.5 kPa (-0.443 to 0.443 in.Hg).
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 G to the evaporative emission canister.
Q: Is the fuel tank pressure between -1.5 to 1.5 kPa (-0.443 to 0.443 in.Hg)?
YES: It can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions. Go to Step 17.
NO: Go to Step 2.
STEP 2. Measure the sensor output voltage at PCM connector B-19 by using check harness special tool MB991923.
1. Disconnect all the connectors from the PCM.
2. Connect special tool MB991923 (check harness) between the PCM and the body-side harness connector.
3. Turn the ignition switch to the "ON" position.
4. Remove the fuel cap.
5. Measure the voltage between terminal 23 and ground.
- The voltage should measure between 2.0 and 3.0 volts.
6. Install the fuel cap.
7. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the measured voltage between 2.0 and 3.0 volts?
YES: Go to Step 16.
NO: Go to Step 3.
STEP 3. Measure the 5-volt reference signal at PCM connector B-19 by using check harness special tool MB991923.
1. Disconnect all the connectors from the PCM.
2. Connect special tool MB991923 (check harness) between the PCM and the body-side harness connector.
3. Turn the ignition switch to the "ON" position.
4. Measure the voltage between terminal 21 and ground.
- The voltage should measure between 4.9 and 5.1 volts.
5. 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 5.
NO: Go to Step 4.
STEP 4. Check PCM connector B-19 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q: Are the connector and terminals in good condition?
YES: Go to Step 16.
NO: Repair or replace the faulty components. Then go to Step 17.
STEP 5. Measure the sensor output voltage at PCM connector B-19 by using check harness special tool MB991923.
1. Disconnect all the connectors from the PCM.
2. Connect special tool MB991923 (check harness) between the PCM and the body-side harness connector.
3. Turn the ignition switch to the "ON" position.
4. Remove the fuel cap.
5. Measure the voltage between terminal 22 and ground.
- The voltage should measure 0.5 volt or less.
6. Install the fuel cap.
7. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the measured voltage 0.5 volt or less?
YES: Go to Step 6.
NO: Go to Step 9.
STEP 6. Measure the signal voltage at fuel tank differential pressure sensor connector D-18.
1. Remove the left rear seat cushion mounting bolts, and lift the left rear seat cushion to tie it to the head restraint.
2. Cut the floor mat and then remove the service hole cover to gain access to the service hole.
NOTE: Push the floor mat to find the notches and cut the floor mat along them.
3. Disconnect fuel tank differential pressure sensor connector D-18.
4. Use special tool MB991658 to connect terminals 1, 2 and 3 of the fuel tank differential pressure sensor connector D-18.
5. Turn the ignition switch to the "ON" position.
6. Remove the fuel cap.
7. Measure the voltage between connector D-18 terminal 1 and ground.
- The voltage should measure between 2.0 and 3.0 volts.
8. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the measured voltage between 2.0 and 3.0 volts?
YES: Go to Step 7.
NO: Go to Step 15.
STEP 7. Check PCM connector B-19, intermediate connector C-32 and fuel tank differential pressure sensor connector D-18 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q: Are the connectors and terminals in good condition?
YES: Go to Step 8.
NO: Repair or replace the faulty components. Then go to Step 17.
STEP 8. Check the harness wire between PCM connector B-19 terminal 23 and fuel tank differential pressure sensor connector D-18 terminal 1 for damage.
Q: Is the harness wire in good condition?
YES: This malfunction is intermittent. Go to Step 17.
NO: Repair the damaged harness wire. Then go to Step
17.
STEP 9. Measure the 5-volt reference signal at fuel tank differential pressure sensor connector D-18.
1. Remove the left rear seat cushion mounting bolts, and lift the left rear seat cushion to tie it to the head restraint.
2. Cut the floor mat and then remove the service hole cover to gain access to the service hole.
NOTE: Push the floor mat to find the notches and cut the floor mat along them.
3. Disconnect fuel tank differential pressure sensor connector D-18.
4. Use special tool MB991658 to connect terminals 1, 2 and 3 of the fuel tank differential pressure sensor connector D-18.
5. Turn the ignition switch to the "ON" position.
6. Measure the voltage between terminal 3 and ground.
- The voltage should measure between 4.9 and 5.1 volts.
7. 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 12.
NO: Go to Step 10.
STEP 10. Check PCM connector B-19, intermediate connector C-32 and fuel tank differential pressure sensor connector D-18 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q: Are the connectors and terminals in good condition?
YES: Go to Step 11.
NO: Repair or replace the faulty components. Then go to Step 17.
STEP 11. Check the harness wire between PCM connector B-19 terminal 21
and fuel tank differential pressure sensor connector D-18 terminal 3 for damage.
Q: Are the harness wires in good condition?
YES: It can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions. Go to Step 17.
NO: Repair the damaged harness wires. Then go to Step
17 .
STEP 12. Measure the fuel tank differential pressure sensor return voltage at intermediate connector D-18.
1. Remove the left rear seat cushion mounting bolts, and lift the left rear seat cushion to tie it to the head restraint.
2. Cut the floor mat and then remove the service hole cover to gain access to the service hole.
NOTE: Push the floor mat to find the notches and cut the floor mat along them.
3. Disconnect fuel tank differential pressure sensor connector D-18.
4. Use special tool MB991658 to connect terminals 1, 2 and 3 of the fuel tank differential pressure sensor connector D-18.
5. Turn the ignition switch to the "ON" position.
6. Measure the voltage between terminal 2 and ground.
- The voltage should measure 0.5 volt or less .
7. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the measured voltage 0.5 volt or less?
YES: Go to Step 13.
NO: Go to Step 17.
STEP 13. Check PCM connector B-19, intermediate connector C-32 and fuel tank differential pressure sensor connector D-18 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q: Are the connectors and terminals in good condition?
YES: Go to Step 14.
NO: Repair or replace the faulty components. Then go to Step 17.
STEP 14. Check the harness wires between PCM connector B-19 terminal 22 and fuel tank differential pressure sensor connector D-18 terminal 2 for damage.
Q: Are the harness wires in good condition?
YES: Go to Step 17.
NO: Repair the damaged harness wires. Then go to Step
17 .
STEP 15. Check fuel tank differential pressure sensor connector D-18 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q: Is the connectors and terminals in good condition?
YES: Replace the fuel tank differential pressure sensor. Go to Step 17.
NO: Repair or replace the faulty components. Then go to Step 17.
STEP 16. Using scan tool MB991958, check data list item 73: 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. Disconnect hose G from the evaporative emission canister, and plug the hose.
3. Turn the ignition switch to the "ON" position.
4. Remove the fuel cap.
5. Set scan tool MB991958 to the data reading mode.
- Item 73, Fuel Tank Differential Pressure Sensor.
- The fuel tank pressure reading on the scan tool should be -1.5 to 1.5 kPa (-0.443 to 0.443 in.Hg).
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 G to the evaporative emission canister.
Q: Is the fuel tank pressure between -1.5 to 1.5 kPa (-0.443 to 0.443 in.Hg)?
YES: It can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions. Go to Step 17.
NO: Replace the PCM. Then go to Step 17.
STEP 17. Perform the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern (Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 15). OBD-II Drive Cycle
2. Read the diagnostic trouble code (DTC).
Q: Is DTC P0451 set?
YES: Repeat the troubleshooting from Step 2.
NO: The procedure is complete.