P0456

System Diagram <Vehicles Without Intake Manifold Tuning System>:

System Diagram <Vehicles With Intake Manifold Tuning System>:

or PCM measure the change of the pressure inside the fuel tank.
- The ECM or PCM turns on the evaporative emission ventilation solenoid valve to shot off the evaporative emission canister outlet port.
- Then the evaporative emission purge solenoid valve is driven to set the fuel system into a negative pressure.
- When the fuel system develops a vacuum of 2 kPa (0.29 psi), the evaporative emission purge solenoid valve is turned "OFF" and the fuel system vacuum is maintained at 2 kPa (0.29 psi).
- The ECM or PCM determines if there is leak in the fuel system by measuring the change of vacuum inside the fuel tank.
- The test is stopped when fuel vapor pressure is judged as too high.

DESCRIPTIONS OF MONITOR METHODS
- Measure reverting pressure after depressurizing by intake manifold negative pressure and detect malfunction if reverting pressure rises largely.

MONITOR EXECUTION
- Once per driving cycle.

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 purge system monitor
- Fuel tank differential pressure sensor 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

DTC SET CONDITIONS

Logic Flow Charts (Monitor Sequence):

Logic Flow Chart

Test Conditions A: At Start up
- The fuel level sensor output voltage is 2.4 - 3.7 volts when the engine starts (i.e. the amount of remaining fuel is 40 - 85 percent)
- Intake air temperature is 36 °C (97 °F) or less when the engine is started.
- The engine coolant temperature 36 °C (97 °F) or less when the engine is started.

Test Conditions B: For Test to Run
- Barometric pressure is above 76 kPa (11 psi).
- The fuel tank temperature is 33 °C (91 °F) or less
- Fuel tank differential pressure sensor output voltage is 1 to 4 volts.

Test Conditions C: For Test to Stop
- Engine coolant temperature is less than 20 °C (68 °F).
- Intake air temperature is less than -10 °C (14 °F).
- When the evaporative emission purge solenoid and evaporative emission ventilation solenoid are closed, the pressure rises higher 324 Pa (0.047 psi).

Judgment Criteria
- Internal pressure of the fuel tank fluctuate 1177 - 1373 Pa (0.171 - 0.199 psi) or more in 128 seconds after the tank and vapor line were closed.
- 10 seconds have elapsed from the start of the previous monitoring.
- Monitoring time: 10 - 14 minutes.

NOTE: The monitoring time depends on the fuel level and the temperature in the fuel tank (10 - 14 minutes.)

OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function - OBD-II Drive Cycle - Procedure 1 - Evaporative Emission System Leak Monitor. OBD-II Drive Cycle Pattern Lists

TROUBLESHOOTING HINTS
The most likely causes for this code to be set are:
- Loose fuel cap.
- Fuel cap relief pressure is incorrect.
- Evaporative emission canister seal is faulty.
- Fuel tank, purge line or vapor line seal failed.
- Evaporative emission ventilation solenoid failed.

OVERVIEW OF TROUBLESHOOTING
- To determine the cause of DTC P0456, a performance test is needed. The performance test uses a mechanical vacuum gauge and scan tool MB991958 set on the fuel tank differential pressure sensor (TANK PRES SNER 73.) The mechanical gauge reading is used to verify scan tool MB991958 reading. A comparison of the mechanical gauge to scan tool MB991958 determines the problem in the system.
- Prior to doing the performance test, several simple inspections are needed to exclude some possibilities of the symptom.

DIAGNOSIS

Required Special Tool:
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: MUT-III USB Cable
- MB991911: MUT-III Main Harness

STEP 1. Using scan tool MB991958, check evaporative emission system monitor test.

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.
- With this monitor, the ECM or PCM automatically increases the engine speed to 1,600 r/min or more. Check that the transaxle is set to "neutral" or "P" position.

1. Connect scan tool MB991958 to the data link connector.
2. Turn the ignition switch to the "ON" position.
3. Erase the DTCs using scan tool MB991958.
4. Check that the fuel cap is securely closed. (Tighten until three clicks are heard.)
5. Start the engine.
6. Select "System Test," and press the "YES" key.
7. Select "Evap Leak Mon," and press the "YES" key.
8. During the monitor, keep the accelerator pedal at the idling position.

NOTE: If the engine speed does not reach 2,000 r/min during the monitor test, adjustment of the Speed Adjusting Screw may be needed. And adjust to the standard value.

9. Keep the engine speed and engine load within the specified range. When the monitor test starts, the "In Progress" item on the scan tool MB991958 will change from "NO" to "YES."
10. Turn the ignition switch to the "LOCK" (OFF) position, and disconnect scan tool MB991958.

Q: What is displayed on the scan tool MB991507?

"Evap Leak Mon. Completed Test Passed": The evaporative emission system is working properly at this time. Explain to customer that improperly tightened fuel cap can cause MIL to turn on, and return the vehicle.

"Evap Leak Mon. Completed. Test Failed and DTCs Set": A malfunction has been detected during the monitor test. Go to Step 2.

"Evap Lead Mon. discontinued. Retest again from the first": The monitor was discontinued for a certain reason (vehicle speed input from computer, engine speed and engine load deviating from specified range). Turn the ignition switch to the "LOCK" (OFF) position once, and repeat the monitoring from the Step 1.

STEP 2. Check evaporative emission purge solenoid for leaks.

1. Remove the battery.
2. Remove the air intake hose. (Refer to Air Cleaner)

3. Disconnect hose C from the evaporative emission purge solenoid side, and connect a hand vacuum pump to the nipple of the evaporative emission purge solenoid.
4. Apply a pressure on the hand vacuum pump, and confirm that air is maintained.
5. Disconnect the hand vacuum pump, and connect hose C to the evaporative emission purge solenoid.

Q: Is the evaporative emission purge solenoid in good condition?

YES: Go to Step 3.

NO: Replace the evaporative emission purge solenoid. Then go to Step 17.

STEP 3. Check for leaks in the evaporator line hose A to hose E or hose B, C, E .
The leakage test with a hand vacuum pump on each hose from hose A to hose E or hose B, C, E .

Q: Are the hoses in good condition?

YES: Go to Step 4.

NO: Replace the inferior hose. Then go to Step 17.

STEP 4. Check the evaporative emission ventilation solenoid using scan tool MB991958. (Actuator test item 29)

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 the hose G from the evaporative emission ventilation solenoid side.

3. Connect the hand vacuum pump to the nipple of the evaporative emission ventilation solenoid from which the hoses have been disconnected.
4. Turn the ignition switch to the "ON" position.
5. Set scan tool MB991958 to actuator test mode for item 29: Evaporative Emission Ventilation Solenoid. When the evaporative emission ventilation solenoid is operated, apply a pressure on the hand vacuum pump and confirm that air is maintained.
6. Turn the ignition switch to the "LOCK" (OFF) position, and disconnect scan tool MB991958.
7. Disconnect the hand vacuum pump, and connect hose G to the evaporative emission canister.

Q: Is the evaporative emission ventilation solenoid in good condition?

YES: Go to Step 5.

NO: Replace the evaporative emission ventilation solenoid. Then go to Step 17.

STEP 5. Pressure test for evaporator line from hose F to hose P.

1. Remove the module bracket mounting bolts, and disconnect hose G from the evaporative emission ventilation solenoid side, and plug the hoses from which the hoses have been disconnected.
2. Confirm that the evaporative emission system pressure pump (Miller number 6872A) is operating properly. Perform the self-test as described in the manufacturer's instructions.

3. Connect an evaporative emission system pressure pump to the fuel filler neck.
4. Pressure test the system to determine whether any leaks are present.

NOTE: "Pressure test" in this procedure refers to the I/M240 Simulation Test (8 simple steps) described in the evaporative emission system pressure pump (Miller number 6872A) manufacturer's instructions located in the lid of the pump box.

Q: Are the evaporator line in good condition?

YES: Go to Step 16.

NO: Go to Step 6.

STEP 6. Pressure test for evaporator line from hose I to hose P.

1. Disconnect hose I from the evaporative emission canister side, and plug the hose from which the pipes have been disconnected.
2. Perform the pressure test again.

Q: Are the evaporator line in good condition?

YES: Go to Step 7.

NO: Go to Step 9.

STEP 7. Check for leaks in the evaporator line hose F to hose H.

1. Remove the fuel tank. (Refer to Fuel Tank)

2. The leakage test with a hand vacuum pump on each hose from hose F to hose H.

Q: Are the hoses in good condition?

YES: Go to Step 8.

NO: Replace that hose, reinstall the fuel tank. (Refer to Fuel Tank) Then go to Step 17.

STEP 8. Check for leaks in the evaporative emission canister.

1. Connect a hand vacuum pump to the vent nipple of the evaporative emission canister.
2. Plug the other two nipples or loop a hose between the other nipples.
3. Apply a vacuum with the hand vacuum pump, and confirm that the applied vacuum does not fluctuate.

Q: Is the evaporation emission canister in good condition?

YES: Go to Step 17.

NO: Replace the evaporative emission canister, reinstall the fuel tank. (Refer to Fuel Tank) Then go to Step 17.

STEP 9. Check for leaks in the evaporator line from hose J and hose K.

1. Remove the fuel filler neck protector. (Refer to Fuel Tank)

2. Disconnect hose J at the liquid separator, and then connect a hand vacuum pump to the hose.

3. Disconnect hose K at the fuel tank side, and then plug the hose.
4. Apply vacuum with the hand vacuum pump, and confirm that the applied vacuum does not fluctuate.

Q: Are the evaporator line in good condition?

YES: Go to Step 10.

NO: Replace that hose, reinstall the fuel filler neck protector. (Refer to Fuel Tank) Then go to Step 17.

STEP10. Check for leaks in the evaporator line hose I, L, M, N and O.

1. Remove the fuel tank and fuel filler neck assembly. (Refer to Fuel Tank)

2. The leakage test with a hand vacuum pump on each hose from hose I, L, M, N and O.

Q: Are the hoses in good condition?

YES: Go to Step 11.

NO: Replace the hose, reinstall the fuel tank and fuel filler neck assembly. (Refer to Fuel Tank) Then go to Step 17.

STEP 11. Check the check valve A.

1. Only when you blow the check valve from the direction shown, it should pass air.
2. When you blow the check valve, air should leak from the check valve body.

Q: Is the check valve A in good condition?

YES: Go to Step 12.

NO: Replace the check valve A, reinstall the fuel tank and fuel filler neck assembly. Then go to Step 17.

STEP 12. Check the check valve B.

1. When you blow the check valve from the arrow direction shown above, it should pass more air.
2. When you blow the check valve from the arrow direction shown below, it should pass less air.
3. When you blow the check valve, air should leak from the check valve body.

Q: Is the check valve B in good condition?

YES: Go to Step 13.

NO: Replace the check valve B, reinstall the fuel tank and fuel filler neck assembly. (Refer to Fuel Tank) Then go to Step 17.

STEP 13. Check for leaks in the evaporator line hose P.

1. The leakage test with a hand vacuum pump on each hose from hose P.

Q: Is the hose in good condition?

YES: Go to Step 14.

NO: Replace the hose, reinstall the fuel tank and fuel filler neck assembly. (Refer to Fuel Tank) Then go to Step 17.

STEP 14. Visually check for cracks in the fuel filler neck assembly.
Visually check for cracks in the fuel filler neck assembly.

Q: Is the fuel filler neck assembly in good condition?

YES: Go to Step 15.

NO: Replace the fuel filler neck assembly, reinstall the fuel tank and fuel filler neck assembly. (Refer to Fuel Tank) Then go to Step 17.

STEP 15. Check for leaks in the fuel tank.

1. Visually check for cracks and leaks, etc.

NOTE: Carefully check the fuel pump assembly and the inner pressure sensor installation section in the fuel tank.

2. Connect an evaporative emission system pressure pump to the leveling valve nipple.

3. Plug the filler hose, feed pipe, return pipe and rollover valve nipple connected to the fuel tank.

NOTE: If these items are not securely plugged here, the fuel could leak in the next step.

4. Apply pressure with the evaporative emission system pressure pump.
5. In the pressurized state, check for the leak by applying soap water, etc. to each section.

Q: Is the fuel tank in good condition?

YES: Go to Step 16.

NO: Replace the fuel tank, reinstall the fuel tank and fuel filler neck assembly. (Refer to Fuel Tank) Then go to Step 17.

STEP 16. Using scan tool MB991958, check evaporative emission system monitor test.

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.
- With this monitor, the ECM or PCM automatically increases the engine speed to 1,600 r/min or more. Check that the transaxle is set to "neutral" or "P" position.

1. Connect scan tool MB991958 to the data link connector.
2. Turn the ignition switch to the "ON" position.
3. Erase the DTCs using scan tool MB991958.
4. Check that the fuel cap is securely closed. (Tighten until three clicks are heard.)
5. Start the engine.
6. Select "System Test," and press the "YES" key.
7. Select "Evap Leak Mon," and press the "YES" key.
8. During the monitor, keep the accelerator pedal at the idling position.

NOTE: If the engine speed does not reach 2,000 r/min during the monitor test, adjustment of the Speed Adjusting Screw may be needed. And adjust to the standard value.

9. Keep the engine speed and engine load within the specified range. When the monitor test starts, the "In Progress" item on the scan tool MB991958 will change from "NO" to "YES."
10. Turn the ignition switch to the "LOCK" (OFF) position. Then disconnect scan tool MB991958.

Q: What is displayed on scan tool MB991958?

"Evap Leak Mon. Completed. Test Passed": The evaporative emission system is working properly at this time. Then go to Step 17 .

"Evap Leak Mon. Completed. Test Failed and DTCs Set": Replace the ECM or PCM . Then go to Step 17.

"Evap Lead Mon. discontinued. Retest again from the first": The monitor was discontinued for a certain reason (vehicle speed input from ECM or PCM , engine speed and engine load deviating from specified range). Turn the ignition switch to the "LOCK" (OFF) position once, and recheck evaporative emission system monitor test.

STEP 17. Test the OBD-II drive cycle.

1. Confirm the repair by performing the appropriate drive cycle (Refer to Diagnostic Function - OBD-II Drive Cycle - Procedure 1 - Evaporative Emission System Leak Monitor ).
2. Read the diagnostic trouble code.

Q: Is diagnostic trouble code P0456 set?

YES: Go to Step 1.

NO: This diagnosis is complete.