DTC P0451: Evaporative Emission Control System Pressure Sensor Range/Performance

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 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)

Check Conditions

Accelerator pedal is not depressed.
Vehicle speed is 1.5 km/h (1 mph) or less.

note

The conditions for deviating from idling operation are as follows:

Vehicle speed is 50 km/h (31 mph) or more.

Judgement Criteria

The drastic pressure fluctuation is detected 20 times or more per engine idling, which is that the fuel tank differential pressure sensor output voltage is 0.2 V or more.
The condition described above is consecutively detected 4 times under the normal driving conditions

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.

OBD-ll DRIVE CYCLE PATTERN

Refer to Diagnostic Function - OBD-ll Drive Cycle - Pattern 16

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 D.
(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 D to the evaporative emission canister.

Q. Is the sensor operating properly?

It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting / Inspection Service Points - How to Cope with Intermittent Malfunctions

Go to Step 2 .

STEP 2. Check harness connector D-17 at fuel tank differential pressure sensor for damage.

Q. Is the harness connector in good condition?

	Then go to Step 3 .

	Repair or replace it. Refer to GROUP 00E, Harness Connector Inspection . Then go to Step 12 .

STEP 3. Measure the sensor supply voltage at fuel tank differential pressure sensor connector D-17 by backprobing.

(1)Do not disconnect the connector D-17.

(2)Turn the ignition switch to the "ON" position.

(3)Measure the voltage between terminal No. 3 and ground by backprobing.

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?

Go to Step 6.

Go to Step 4.

STEP 4. Check harness connector B-109 at ECM for damage.

Q. Is the harness connector in good condition?

	Go to step 5.

	Repair or replace it. Refer to GROUP 00E, Harness Connector Inspection . Then go to Step 12.

STEP 5. Check for harness damage between fuel tank differential pressure sensor connector D-17 (terminal No. 3) and ECM connector B-109 (terminal No. 114).

note

Check harness after checking intermediate connector C-39. If intermediate connector is damaged, repair or replace it. Refer to GROUP 00E, Harness Connector Inspection

. Then go to Step 12.

Q. Is the harness wire in good condition?

	Go to Step 11.

	Repair it. Then go to Step 12.

STEP 6. Measure the ground voltage at fuel tank differential pressure sensor connector D-17 by backprobing.

(1)Do not disconnect the connector D-17.

(2)Turn the ignition switch to the "ON" position.

(3)Measure the voltage between terminal No. 2 and ground by backprobing.

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?

Go to Step 9.

Go to Step 7.

STEP 7. Check harness connector B-109 at the ECM for damage.

Q. Is the harness connector in good condition?

	Go to Step 8.

	Repair or replace it. Refer to GROUP 00E, Harness Connector Inspection . Then go to Step 12.

STEP 8. Check for harness damage between fuel tank differential pressure sensor connector D-17 (terminal No. 2) and ECM connector B-109 (terminal No. 113).

note

Check harness after checking intermediate connector C-39. If intermediate connector is damaged, repair or replace it. Refer to GROUP 00E, Harness Connector Inspection

. Then go to Step 12.

Q. Is the harness wire in good condition?

	Go to Step 11.

	Repair it. Then go to Step 12.

STEP 9. Check harness connector B-109 at ECM for damage.

Q. Is the harness connector in good condition?

	Go to Step 10.

	Repair or replace it. Refer to GROUP 00E, Harness Connector Inspection . Then go to Step 12.

STEP 10. Check for harness damage between fuel tank differential pressure sensor connector D-17 (terminal No. 1) and ECM connector B-109 (terminal No. 112).

note

Check harness after checking intermediate connector C-39. If intermediate connector is damaged, repair or replace it. Refer to GROUP 00E, Harness Connector Inspection

. Then go to Step 12.

Q. Is the harness wire in good condition?

	Go to Step 11.

	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 test drive with the drive cycle pattern. Refer to Diagnostic Function. OBD-II Drive Cycle. Pattern 16

(3)Check the diagnostic trouble code (DTC).

Q. Is DTC P0451 set?

	Replace the ECM. When the ECM is replaced, register the ID code. Refer to GROUP 42B, Diagnosis - ID Code Registration Judgment Table <Vehicles with KOS> or GROUP 42C, Diagnosis - ID Code Registration Judgment Table <Vehicles with WCM> . Then go to Step 12 .

	The inspection is complete.

STEP 12. 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 16

(2)Check the diagnostic trouble code (DTC).

Q. Is DTC P0451 set?

	Repeat the troubleshooting.

	The procedure is complete.