DTC P0456: Evaporative Emission Control System Leak Detected (Very Small Leak)

TECHNICAL DESCRIPTION

The ECM monitors the Evaporative Emission (EVAP) System pressure.
The ECM controls the evaporative emission ventilation solenoid. It closes the evaporative emission ventilation solenoid to seal the evaporative emission canister side of the system.
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 determines whether there is a leak in the EVAP system by monitoring the vacuum inside the fuel tank.
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 tank temperature 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

DTC SET CONDITIONS

Logic Flow Chart (Monitor Sequence)

Check Conditions

Engine coolant temperature is less than 36°C (97°F) when the engine is started.
Intake air temperature is less than 36°C (97°F) when the engine is started.
Engine coolant temperature is more than 20°C (68°F).
When the evaporative emission purge solenoid and evaporative emission ventilation solenoid are closed, the change of the pressure in the fuel tank is less than 324 Pa (0.09 in.Hg).
Amount of remaining fuel is 40 - 85 percent of capacity when the engine is started.
Barometric pressure is more than 76 kPa (22.4 in.Hg).
Intake air temperature is more than -10°C (14°F).
Fuel temperature is less than 33°C (91°F).
Fuel tank differential pressure sensor output voltage is between 1.0 and 4.0 volts.
At least 10 seconds have passed since the last monitor was complete.
Monitoring time: 10 - 14 minutes

Judgement Criterion

In case the amount of change in the pressure that is monitored for a given length of time inside the tank is beyond the specified value after sealing off the fuel tank and the vapor line.

note The specified value varies depending on the fuel temperature and fuel level.

FAIL-SAFE AND BACKUP FUNCTION

None

OBD-ll DRIVE CYCLE PATTERN

Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 5

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 (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 the 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.
During this test, the ECM will automatically increase the engine speed to 1,600 r/min or greater. Check that the transaxle is set to "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 "Special Function"
(7)Select "Evap Leak Monitor"
(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?

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, 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.

STEP 2. Test check valve.

(1)Check valve is a one-way check valve.

(2)Check valve should allow air to flow in only one direction.

Q. Does check valve allow air to pass in one direction only?

Go to Step 3 .

Replace check valve. Then go to Step 14 .

STEP 3. Check for leaks in evaporative emission hoses A and B.

Use a hand vacuum pump to test each hose A and B.

Q. Do the hoses hold vacuum?

Go to Step 4 .

Replace any damaged hose. Then go to Step 14 .

STEP 4. Check the evaporative emission purge solenoid for leaks.

Refer to GROUP 17, Emission Control - Evaporative Emission Control System - Evaporative Emission Purge Solenoid Check

Q. Is the evaporative emission purge solenoid operating properly?

	Go to Step 5 .

	Replace the evaporative emission purge solenoid. Then go to Step 14 .

STEP 5. Check for leaks in evaporative emission hoses C and D.

Use a hand vacuum pump to test each hose C and D.

Q. Do the hoses hold vacuum?

Go to Step 6 .

Replace any damaged hose. Then go to Step 14 .

STEP 6. Using scan tool MB991958, check actuator test item 15: Evaporative emission ventilation solenoid.

(1)Remove the canister cover.

(2)Remove the evaporative emission ventilation solenoid. Do not disconnect the connector.

(3)Connect the hose of the hand vacuum pump to the canister side nipple of the evaporative emission ventilation solenoid.
(4)Turn the ignition switch to the "ON" position.
(5)Set scan tool MB991958 to actuator test mode.

Item 15: Evaporative Emission Ventilation Solenoid.

While the evaporative emission ventilation solenoid is energized, operate the hand vacuum pump and confirm that the solenoid holds vacuum.

(6)Turn the ignition switch to the "LOCK" (OFF) position.
(7)Disconnect the hand vacuum pump, and reinstall the evaporative emission ventilation solenoid.
(8)Reinstall the canister cover.

Q. Did the evaporative emission ventilation solenoid hold vacuum?

Go to Step 7 .

Replace the evaporative emission ventilation solenoid. Then go to Step 14 .

STEP 7. Perform the pressure test on the evaporative emission system.

(1)Disconnect hose E from the canister while holding the release buttons indicated in the illustration pressed by fingers.

(2)Plug the disconnected end of hose E.
(3)Confirm that the evaporative emission system pressure pump (Miller number 6872A) is operating properly. Perform the self-test as described in the pump manufacturer’s instructions.
(4)Remove the fuel cap.

(5)Connect the evaporative emission system pressure pump (Miller number 6872A) to the fuel tank filler tube by using fuel tank adapter (MLR-8382).
(6)Pressure test the system to determine whether any leaks are present.

note

The "Pressure test" in this procedure refers to the I/M240 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.

(7)Remove the evaporative emission system pressure pump (Miller number 6872A) and the fuel tank adapter (MLR-8382), and reinstall the fuel cap.
(8)Connect hose E to the evaporative emission canister.

Q. Is the evaporative emission system line free of leaks?

Go to Step 12 .

Go to Step 8 .

STEP 8. Check for leaks in evaporative emission hoses E and F.

(1)Use a hand vacuum pump to test each hose E and F.

Q. Do the hoses hold vacuum?

Go to Step 9 .

Replace any damaged hose. Then go to Step 14 .

STEP 9. Check for leaks in evaporative emission hoses G and H.

(1)Remove the fuel tank assembly.

(2)Use a hand vacuum pump to test each hose G and H.

Q. Do the hoses hold vacuum?

Go to Step 10.

Replace any damaged hose and reinstall the fuel tank assembly. Then go to Step 14 .

STEP 10. Check for leaks in evaporative emission hoses I and J.

(1)Remove the fuel tank assembly.

(2)Use a hand vacuum pump to test each hose I and J.

Q. Do the hoses hold vacuum?

Go to Step 11 .

Replace any damaged hose and reinstall the fuel tank assembly. Then go to Step 14 .

STEP 11. 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 module and the fuel tank differential pressure sensor installation in the fuel tank.

(2)Connect the evaporative emission system pressure pump (Miller number 6872A) to the fuel filler hose.

(3)Plug the hose and the nipple shown in the illustration.

note

If these items are not securely plugged now, 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. Are any leaks found?

YES <When there is a leak from the attachment points of the fuel pump module, fuel tank differential pressure sensor, fuel level sensor or leveling valve.>

: Reassemble the leaked parts and check again that there are no leaks. Then reinstall the fuel tank. Then go to Step 14 .

YES <When there is a leak from the fuel tank.>

: Replace the fuel tank. Then go to Step 14 .

When there is no leak, reinstall the fuel tank. Then go to Step 13 .

STEP 12. Check the evaporative emission canister for vacuum leaks.

(1)Connect a hand vacuum pump to the evaporative emission canister 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 remove the plugs.

Q. Is the evaporative emission canister in good condition?

Go to Step 13 .

Replace the evaporative emission canister. Then go to Step 14 .

STEP 13. Using scan tool MB991958, check the evaporative emission system monitor test.

caution

During this test, the ECM automatically increases the engine speed to 1,600 r/min or greater. Check that the transaxle is set to "P" position.

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

(2)Erase the DTCs using scan tool MB991958.

(3)Check that the fuel cap is securely closed (Tighten until three clicks are heard).

(4)Start the engine.

(5)Select "Special Function"

(6)Select "Evap Leak Monitor"

(7)During the test, keep the accelerator pedal at the idle position.

(8)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".

(9)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is "Evap Leak Mon. Completed. Test Failed and DTCs Set" displayed on scan tool MB991958?

	Replace the ECM. When the ECM is replaced, register the ID code. Refer to GROUP 42B, ID Code Registration Judgment Table <Vehicles with KOS> or GROUP 42C, ID Code Registration Judgment Table <Vehicles with WCM> . Then go to Step 14 .

	NO <"Evap Leak Mon. Completed. Test Passed" is displayed on scan tool MB991958.> : The evaporative emission system is working properly at this time. Go to Step 14 .

	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.

STEP 14. Test 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 5

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

Q. Is DTC P0456 set?

	Retry the troubleshooting.

	The inspection is complete.