Part 1 of 2
DTC P0451: Evaporative Emission Control 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 ECM (terminal 42)
- The fuel tank differential pressure sensor (terminal 1) returns a voltage signal to the ECM (terminal 93)
TECHNICAL DESCRIPTION
- The ECM
- The ECM
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
- Immediately.
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 level sensor monitor
- Fuel temperature sensor monitor
Sensor (The sensors below are determined to be normal)
- Volume airflow sensor
- Barometric pressure sensor
- Intake air temperature sensor
- Engine coolant temperature sensor
- Accelerator pedal position sensor
Logic Flow Charts (Monitor Sequence):
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 Criterion
- 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 Pattern Lists.
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 ECM
OVERVIEW OF TROUBLESHOOTING
- DTC P0451 can be set by a faulty fuel tank differential pressure sensor or related circuit, or ECM
- 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 (MUT-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: MUT-III USB Cable
- MB991911: MUT-III Main Harness B
- MB991658: Test Harness Set
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 inHg).
6. Connect an evaporative emission system pressure pump (Miller number 6872A) to the fuel filler neck 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. Disconnect the evaporative emission system pressure pump, and reinstall the fuel cap.
9. Connect hose G to the canister.
Q: Is the fuel tank pressure between -1.5 and 1.5 kPa (- 0.443 and 0.443 inHg)?
YES: It can be assumed that this malfunction is intermittent Then go to Step 27
NO: Go to Step 2.
STEP 2. Measure the signal voltage at intermediate connector D-14 by backprobing.
1. Disconnect hose G from the evaporative emission canister side, and plug the hose.
2. Remove the rear seat cushion.
3. Pull up the carpet.
4. Turn the ignition switch to the "ON" position.
5. Remove the fuel cap.
6. Measure the voltage between connector D-14 terminal 11 and ground by backprobing.
- The voltage should measure between 2.0 and 3.0 volts.
7. Connect an evaporative emission system pressure pump (Miller number 6872A) to the fuel filler neck and pressurize the fuel tank.
- The fuel tank pressure reading should increase.
8. Turn the ignition switch to the "LOCK" (OFF) position.
9. Disconnect the evaporative emission system pressure pump, and reinstall the fuel cap.
10. Connect hose G to the canister.
Q: Is the measured voltage between 2.0 and 3.0 volts?
YES: Go to Step 3.
NO: Go to Step 7.
STEP 3. Measure the signal voltage at ECM connector C- 115
1. Do not disconnect ECM connector C-115
2. Disconnect hose G from the evaporative emission canister side, and plug the hose.
3. Turn the ignition switch to the "ON" position.
4. Remove the fuel cap.
5. Measure the voltage between connector C-115 terminal 93
-
6. Connect an evaporative emission system pressure pump (Miller number 6872A) to the fuel filler neck and pressurize the fuel tank.
- The fuel tank pressure reading should increase.
7. Turn the ignition switch to the "LOCK" (OFF) position.
8. Disconnect the evaporative emission system pressure pump, and reinstall the fuel cap.
9. Connect hose G to the canister.
Q: Is the measured voltage between 2.0 and 3.0 volts?
YES: Go to Step 4.
NO: Go to Step 5.
STEP 4. Check ECM connector C-115
Q: Are the connectors and terminal in good condition?
YES: Go to Step 26.
NO: Repair or replace the damaged components. Then go to Step 27.
STEP 5. Check intermediate connectors C-124, C-127, D-14 and ECM connector C-115
Q: Are the connectors and terminals in good condition?
YES: Go to Step 6.
NO: Repair or replace the faulty component. Go to Step 27.
STEP 6. Check the harness wire between ECM connector C-115 terminal 93
Q: Is the harness wire in good condition?
YES: It can be assumed that this malfunction is intermittent. Then go to Step 27.
NO: Repair the damaged harness wire. Then go to Step 27.
STEP 7. Measure the 5-volt reference signal 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 connector D-14 terminal 9 and ground.
- The voltage should measure 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 11.
NO: Go to Step 8.
STEP 8. Measure the 5-volt reference signal at ECM connector C-117
1. Do not disconnect ECM connector C-117
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between connector C-117 terminal 42
- The voltage should measure 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 9.
NO: Go to Step 25.
STEP 9. Check intermediate connectors C-105, C-124, C- 127, and D-14 and ECM connector C-117
Q: Are the connectors and terminals in good condition?
YES: Go to Step 10.
NO: Repair or replace the damaged components. Then go to Step 27.
STEP 10. Check the harness wire between ECM connector C-117
Q: Is the harness wire in good condition?
YES: It can be assumed that this malfunction is intermittent. Then go to Step 27.
NO: Repair the damaged harness wire. Then go to Step 27.
STEP 11. Check the sensor ground 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 connector D-14 terminal 10 and ground by backprobing.
- The voltage should measure 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 15
NO: Go to Step 12.