P0456
DTC P0456: Evaporative Emission Control System Leak Detected (Very Small Leak)System Diagram:
TECHNICAL DESCRIPTION
- The ECM
- The ECM
- The evaporative emission purge solenoid is opened to allow manifold vacuum to create low pressure (vacuum) in the EVAP system.
- When the EVAP system develops a vacuum of 2 kPa (0.29 psi), the evaporative emission purge solenoid is closed and the fuel system vacuum is maintained at 2 kPa (0.29 psi).
- The ECM
- The test is stopped when fuel vapor pressure exceeds predetermined limits.
- The test is stopped when fuel vapor pressure exceeds predetermined limits.
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
Logic Flow Chart (Monitor Sequence):
LOGIC FLOW CHARTS (Monitor Sequence)
DTC SET CONDITIONS
Check Conditions A: At Start up
- 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. The fuel level sensor output voltage is 2.4 - 3.7 volts when the engine starts and the amount of remaining fuel is 40 - 85 percent of capacity.
Check Conditions B: For Test to Run
- Barometric pressure is greater than 76 kPa (11 psi).
- The fuel temperature is 33 °C (91 °F) or less.
- Fuel tank differential pressure sensor output voltage is 1 to 4 volts.
Check Conditions C: For Test to Stop
- Engine coolant temperature is greater than 20 °C (68 °F).
- Intake air temperature is greater than -10 °C (14 °F).
- When the evaporative emission purge solenoid and evaporative emission ventilation solenoid are closed, the pressure rises in the fuel tank is less than 324 Pa (0.047 psi).
- 10 seconds have elapsed from the start of the previous monitoring.
- Monitoring time: 10 - 14 minutes.
Judgment Criteria
- Internal pressure of the fuel tank has changed greater than 1,177 - 1,373 Pa (0.177 - 0.199 psi) in 128 seconds after the tank and vapor line were closed.
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.
- Malfunction of the evaporative emission canister seal.
- Malfunction of the fuel tank, purge line or vapor line seal.
- Malfunction of the evaporative emission ventilation solenoid.
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
STEP 1. Using scan tool MB991958, check the EVAP 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.
- During this test, the ECM
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."
7. Select "Evap Leak Mon."
8. During this test, keep the accelerator pedal at the idle position.
9. Keep the engine speed and engine load within the specified range. When the monitor test starts, the "In Progress" item on 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: Is "Evap Leak Mon. Completed. Test Failed and DTCs Set" displayed on scan tool MB991958?
YES: A malfunction has been detected during the monitor test. Refer to the Diagnostic Trouble Code Chart and diagnose any other DTCs that are set. If no other DTC's have been set, then go to Step 2.
NO <"Evap Leak Mon. Completed. Test Passed" is displayed on scan tool MB991958.>: The evaporative emission system is working properly at this time. Explain to the customer that an improperly tightened fuel cap can cause the MIL to illuminate. Return the vehicle to the customer.
NO <"Evap Leak Mon. Discontinued. Retest again from the first" is displayed on scan tool MB991958.>: The EVAP monitor has been interrupted during the test. Turn the ignition switch to the "LOCK" (OFF) position once, and repeat the monitoring from Step 1.
STEP 2. Check the evaporative emission purge solenoid for leaks.
1. Disconnect hose C from the evaporative emission purge solenoid and connect a hand vacuum pump to the nipple of the evaporative emission purge solenoid.
2. Use the hand vacuum pump to confirm that the evaporative emission purge solenoid holds vacuum.
3. Disconnect the hand vacuum pump, and connect hose C to the evaporative emission purge solenoid.
Q: Does the evaporative emission purge solenoid hold vacuum?
YES: Go to Step 3.
NO: Replace the evaporative emission purge solenoid. Then go to Step 15.
STEP 3. Check for leaks in evaporative emission system hoses A through C.
Use a hand vacuum pump to test each hose from hose A to hose C.
Q: Do the hoses hold vacuum?
YES: Go to Step 4.
NO: Replace any damaged hose. Then go to Step 15.
STEP 4. Using scan tool MB991958, check data list item 29: Evaporative Emission Ventilation Solenoid.
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 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 MB991958 to actuator test mode.
- Item 29: Evaporative Emission Ventilation Solenoid.
- While the evaporative emission ventilation solenoid is energized, operate the hand vacuum pump and confirm that the solenoid holds vacuum.
5. Turn the ignition switch to the "LOCK" (OFF) position, and disconnect scan tool MB991958.
6. Disconnect the hand vacuum pump, and connect hose F to the evaporative emission canister.
Q: Did the evaporative emission ventilation solenoid hold vacuum?
YES: Go to Step 6.
NO: Go to Step 5.
STEP 5. Check for leaks in evaporative emission hose F.
Perform a leakage test using a hand vacuum pump on hose F.
Q: Do the hose hold vacuum?
YES: Replace the evaporative emission ventilation solenoid. Then go to Step 15.
NO: Replace hose F. Then go to Step 15.
STEP 6. Check for leaks in evaporative emission system hoses D and E.
Perform a leakage test with a hand vacuum pump on each hose between hose D and hose E.
Q: Do the hoses hold vacuum?
YES: Go to Step 7.
NO: Replace the damaged hose. Then go to Step 15.
STEP 7. Pressure test for leaks in evaporative system lines from hose G through the fuel tank to hose Q.
1. Disconnect hose G from the canister, and plug hose G securely.
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 the evaporative emission system pressure pump to the fuel filler neck.
4. Pressure test the system to determine whether any leaks are present.
NOTE: The "Pressure test" in this procedure refers to the I/M 240 Simulation Test. The eight steps of this test are described in the manufacturer's instructions for the evaporative emission system pressure pump, Miller number 6872A.
5. Disconnect the evaporative emission system pressure pump, and reinstall the fuel cap.
6. Connect hose G to the canister.
Q: Is the evaporative emission system line free of leaks?
YES: Go to Step 13.
NO: Go to Step 8.
STEP 8. Check for leaks in evaporative emission hoses G, I, J and K.
1. Remove the fuel filler neck protector. (Refer to Fuel Tank.)
2. Perform a leakage test with a hand vacuum pump on each hose: G, I, J and K.
Q: Do the hoses hold vacuum?
YES: Go to Step 9.
NO: Replace any damaged hose, and reinstall the fuel filler neck protector. Refer to Fuel Tank. Then go to Step 15.
STEP 9. Test check valve A.
1. Check valve A is a one-way check valve.
2. Check valve A should allow air to flow in only one direction.
Q: Does check valve A allow air to pass in one direction only?
YES: Go to Step 10.
NO: Replace check valve A, and reinstall the fuel filler neck protector. Refer to Fuel Tank. Then go to Step 15.
STEP 10. Check for leaks in evaporative emission hoses H, L, M, N, 0, P, and Q.
1. Remove the fuel tank. (Refer to Fuel Tank.)
2. Perform a leakage test with a hand vacuum pump on each hose H, L, M, N, 0, P and Q.
Q: Do the hoses hold vacuum?
YES: Go to Step 11.
NO: Replace any damaged hose, and reinstall the fuel tank. Refer to Fuel Tank. Then go to Step 15.
STEP 11. Test check valve B.
1. Check valve B is a one-way check valve.
2. Check valve B should allow air to flow in only one direction.
Q: Does check valve B allow air to pass in one direction only?
YES: Go to Step 12.
NO: Replace check valve B, and reinstall the fuel tank and the fuel filler neck protector. Refer to Fuel Tank. Then go to Step 15.
STEP 12. Check for leaks in the fuel tank.
1. Visually check for cracks or other leaks in the fuel tank.
NOTE: Carefully check the fuel pump assembly and the differential pressure sensor installation in the fuel tank.
2. Connect an evaporative emission system pressure pump (Miller number 6872A) to the filler hose.
3. Plug the fuel pump feed nipple, hose H, hose L and hose Q connected to the fuel tank.
NOTE: If these items are not securely plugged here, the fuel could leak in the next step.
4. Pressurize the fuel tank with the evaporative emission system pressure pump.
5. In the pressurized state, check for leaks by applying a soapy water solution to each section and look for bubbles.
Q: Is any leaks found?
YES
YES
NO: When there is no leak, reinstall the fuel tank (Refer to Fuel Tank). Then go to Step 14.
STEP 13. Check the evaporative emission canister for vacuum 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: Does the evaporative emission canister hold vacuum?
YES: Go to Step 13.
NO: Replace the evaporative emission canister. Refer to Evaporative Emission Canister and Fuel Tank Pressure Relief Valve. Then go to Step 15.
STEP 14. Using scan tool MB991958, check the EVAP 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.
- During this test, the ECM
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."
7. Select "Evap Leak Mon."
8. During the test, keep the accelerator pedal at the idle position.
9. Keep the engine speed and engine load within the specified range. When the monitor test starts, the "In Progress" item on scan tool MB991958 will change from "NO" to "YES."
10. Turn the ignition switch to the "LOCK" (OFF) position. Disconnect scan tool MB991958.
Q: Is "Evap Leak Mon. Completed. Test Failed and DTCs Set" displayed on scan tool MB991958?
YES: Replace the ECM
NO <"Evap Leak Mon. Completed. Test Passed" is displayed on scan tool MB991958.>: The evaporative emission system is working properly at this time. Then go to Step 15.
NO <"Evap Leak Mon. Discontinued. Retest again from the first" is displayed on scan tool MB991958.>: The EVAP monitor has been interrupted during the test. Turn the ignition switch to the "LOCK" (OFF) position once, and repeat the monitoring from Step 14.
STEP 15. Perform 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). OBD-II Drive Cycle Pattern Lists
2. Read the diagnostic trouble code (DTC).
Q: Is DTC P0456 set?
YES: Repeat the troubleshooting from Step 1.
NO: The procedure is complete.