P0456
System Diagram:
TECHNICAL DESCRIPTION
- To judge if there is leak in the fuel system, ECM
- The ECM
- 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
- The test is stopped when fuel vapor pressure is judged as too high.
DTC SET CONDITIONS
Test Conditions A: At Start up
- Intake air temperature is 33 °C (91 °F) or less when the engine is started.
- The engine coolant temperature 33 °C (91 °F) or less when the engine is started.
- 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)
Test Conditions B: For Test to Run
- Engine coolant temperature is higher than 20 °C (68 °F).
- Barometric pressure is above 76 kPa (11 psi).
- Volumetric efficiency is between 20 and 80 percent.
- The fuel temperature is 33 °C (91 °F) or less
Test Conditions C: For Test to Stop
- Intake air temperature is higher than -10 °C (14 °F).
- When the evaporative emission purge solenoid and evaporative emission ventilation solenoid valve are closed, the pressure rises within 324 Pa (0.047 psi).
- Fuel tank differential pressure sensor output voltage is 1 to 4 volts.
Judgment Criteria
- Internal pressure of the fuel tank fluctuate 1177 - 1373 Pa (0.177 - 0.199 psi) or more in 10 seconds after the tank and vapor line were closed.
NOTE: The monitoring time depends on the fuel level and the temperature in the fuel tank (10 - 14 minutes.)
Before the next monitoring, it takes 10 seconds or more.
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 valve 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 MB991502 set on the fuel tank differential pressure sensor (TANK PRES SNER 73.) The mechanical gauge reading is used to verify scan tool MB991502 reading. A comparison of the mechanical gauge to scan tool MB991502 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:
- MB991502: Scan Tool (MUT-II)
CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
In this procedure, scan tool MB991502 should be used in the metric mode (showing the value in kPa). If not, set scan tool MB991502 by selecting the "System Setup" at the main menu.
STEP 1. Using scan tool MB991502, check evaporative emission system monitor test.
CAUTION:
- To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
- With this monitor, the ECM
1. Connect scan tool MB991502 to the data link connector.
2. Check the fuel cap is securely closed. (Tighten until three clicks are heard.)
NOTE: The fuel overflow limiter valve plunger moves upward when the flapper is pushed.
3. With the gear selector lever in the "P" position, start the engine and run at idle.
4. Set scan tool MB991502 to system test mode for item: Evap Leak Mon. and During monitor, keep the accelerator pedal at idling position.
5. Turn the ignition switch to the "LOCK" (OFF) position.
Q: What is displayed on scan tool MB991502?
"Evap Leak Mon. Completed. Test Passed" : The evaporative emission system is working properly at this time. It is presumed that this malfunction is caused by improperly tightened fuel cap.
"Evap Leak Mon. Completed. Test Failed and DTCs Set" : 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 ECM
STEP 2. Check solenoid valve for leaks of the purge control.
1. Disconnect hose C from the evaporative emission purge solenoid valve side, and connect a hand vacuum pump.
2. Apply a pressure on the hand vacuum pump and confirm that air is maintained.
3. Disconnect the hand vacuum pump, and connect hose C to the evaporative emission purge solenoid valve.
Q: Is the solenoid valve in good condition?
YES: Go to Step 3.
NO: Replace the evaporative emission purge solenoid valve. Then go to Step 15.
STEP 3. Check for leaks in the evaporator line hose A to hose C.
Q: Are the hoses in good condition?
YES: Go to Step 4.
NO: Replace the inferior hose. Then go to Step 15.
STEP 4. Check the evaporative emission ventilation solenoid valve and hose F using scan tool MB991502.
CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
1. Connect scan tool MB991502 to the data link connector
2. Disconnect hose F from the evaporative emission canister side, and connect a hand vacuum pump.
3. Turn the ignition switch to the "ON" position.
4. Set scan tool MB991502 to actuator test mode for item 29: Evaporative Emission Ventilation Solenoid Valve. When the evaporative emission ventilation solenoid valve is operated, apply a pressure on the hand vacuum pump and confirm that air is maintained.
5. Turn the ignition switch to the "LOCK" (OFF) position.
6. Disconnect the hand vacuum pump, and connect hose F to the evaporative emission canister.
Q: Is the solenoid valve in good condition?
YES: Go to Step 6.
NO: Go to Step 5.
STEP 5. Check for leaks in the evaporator line hose F.
Q: Are the hoses in good condition?
YES: Replace the evaporative emission ventilation solenoid valve. Then go to Step 15
NO: Replace the inferior hose. Then go to Step 15.
STEP 6. Check for leaks in evaporator line hose D to hose E.
Q: Are the hoses in good condition?
YES: Go to Step 7.
NO: Replace the inferior hose. Then go to Step 15.
STEP 7. Pressure test for leaks in evaporator line from hose G to hose P and the fuel tank.
1. Disconnect hose G from the canister side, and plug the hose.
2. Remove the fuel cap.
3. Connect the evaporative emission system pressure pump to the fuel filler neck.
4. Apply a pressure on the evaporative emission system pressure pump, and confirm that air is maintained.
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) manufacture's instructions located in the lid of the pump box.
5. Disconnect the evaporative emission system pressure pump, and reinstall the fuel cap.
6. Connect hose G to the evaporator line.
Q: Is air maintained?
YES: Go to Step 14.
NO: Go to Step 8.
STEP 8. Check for leaks in the evaporator line hoses G, I, J and K.
1. Remove the fuel filler neck protector. (Refer to Fuel Tank.)
2. The leakage test with a hand vacuum pump on each hose from hoses G, I, J and K.
Q: Are the hoses in good condition?
YES: Go to Step 9.
NO: Replace the inferior hose, and reinstall the fuel filler neck protector. Refer to Fuel Tank. Then go to Step 15.
STEP 9. Check 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, on air should leak from the check valve body.
Q: Is check valve A in good condition?
YES: Go to Step 10.
NO: Replace it, and reinstall the fuel filler neck protector. Refer to Fuel Tank. Then go to Step 15.
STEP 10. Check for leaks in the evaporator line from hoses H, L, M, N, O and P.
Remove the fuel tank. (Refer to Fuel Tank.)
Q: Are the hoses in good condition?
YES: Go to Step 11.
NO: Replace the inferior hose, and reinstall the fuel tank. Refer to Fuel Tank. Then go to Step 15.
STEP 11. 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, on air should leak from the check valve body.
Q: Is the check valve B in good condition?
YES: Go to Step 12.
NO: Replace it, and reinstall the fuel tank and the fuel filler neck protector. Refer to Fuel Tank. Then go to Step 15.
STEP 12. Check the fuel tank for leaks.
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 the evaporative emission system pressure pump to the filler hose.
3. Plug the fuel pump feed nipple, return hose, hose L and hose H 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 leaks by applying soap water, etc. to each section.
Q: Are there any leaks?
There are leaks at the fuel pump assembly, the fuel tank differential pressure sensor, leveling valve or the fuel tank rollover valve installation section.: After reassemble the leaked parts, check again that there are no leaks. Then reinstall the fuel tank. Then go to Step 15.
There are leaks at the fuel tank.: Replace the fuel tank. Refer to Fuel Tank. Then go to Step 15.
There are no leaks.: Reinstall the fuel tank. Refer to Fuel Tank. Then go to Step 13.
STEP 13. Using scan tool MB991502, check evaporative emission system monitor test.
CAUTION:
- To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
- With this monitor, the ECM
1. Connect scan tool MB991502 to the data link connector.
2. Check the fuel cap is securely closed. (Tighten until three clicks are heard.)
NOTE: The fuel overflow limiter valve plunger moves upward when the flapper is pushed.
3. With the gear selector lever in the "P" position, start the engine and run at idle.
4. Set scan tool MB991502 to system test mode for item: Evap Leak Mon. and During monitor, keep the accelerator pedal at idling position.
5. Turn the ignition switch to the "LOCK" (OFF) position.
Q: What is displayed on scan tool MB991502?
"Evap Leak Mon. Completed. Test Passed" : The evaporative emission system is working properly at this time. Then go to Step 15
"Evap Leak Mon. Completed. Test Failed and DTCs Set": Replace the ECM
"Evap Lead Mon. discontinued. Retest again from the first" : The monitor was discontinued for a certain reason (vehicle speed input from ECM
STEP 14. Check the evaporative emission canister for leaks.
1. Disconnect hoses E, F and G from the evaporative emission canister side, and connect a hand vacuum pump to the evaporative emission canister instead of hose E, and plug the other nipples.
2. Apply a pressure on the hand vacuum pump, and confirm that air is maintained.
3. Disconnect the hand vacuum pump, and connect hoses E, F and G to the canister.
Q: Is the evaporative emission canister in good condition?
YES: Go to Step 13.
NO: Replace the canister. Refer to Evaporative Emission Canister and Fuel Tank Pressure Relief Valve. Then go to Step 15.
STEP 15. Test the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern. Refer to, Procedure 1 - Evaporative Emission Control 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.