P0456
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.
DTC SET CONDITIONS
Test Conditions:
- Fuel level sensor output voltage is 2.4 - 3.7 volts when the engine is started, and the amount of remaining fuel is 40 - 85 percent of capacity.
- 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 greater than 20 °C (68 °F).
- Intake air temperature is greater than -10 °C (14 °F).
- Fuel temperature is less than 33 °C (91 °F).
- Barometric pressure is greater than 76 kPa (11 psi).
- Fuel tank differential pressure sensor output voltage is 1 - 4 volts.
- 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.
- Only one monitor during one drive cycle.
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 leaking.
- Fuel tank, purge line or vapor line seal is leaking.
- Evaporative emission ventilation solenoid dose not seal.
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 to the data reading mode for the fuel tank differential pressure sensor (TANK PRES SNER 73). The mechanical gauge reading is used to verify the scan tool reading. A comparison of the mechanical gauge and scan tool MB991502 determines whether there is problem in the system.
- Prior to doing the performance test, ensure that the fuel cap is closed securely. Inspect all EVAP system hoses and tubes for damage.
DIAGNOSIS
Required Special Tool:
- MB991502: Scan Tool (MUT-II)
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 "LOCK11 (OFF) position before connecting or disconnecting scan tool MB991502.
- During this test, the ECM
1. Connect scan tool MB991502 to the data link connector.
2. Turn the ignition switch to the "ON" position.
3. Erase the DTCs using scan tool MB991502. (Refer to Trouble Code Diagnosis - How to Read and Erase Diagnostic Trouble Codes).
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 rpm during the monitor test, adjust the Speed Adjusting Screw (Refer to On-vehicle Service - Basic Idle Speed Adjustment), 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 MB991502 will change from "NO" to "YES".
10. Turn the ignition switch to the "LOCK" (OFF) position, and disconnect scan tool MB991502.
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 an improperly tightened fuel cap can cause MIL to turn on. Return the vehicle to the customer.
"Evap Leak Mon. Completed. Test Failed and DTCs Set": A malfunction has been detected during the monitor test. Refer to Diagnostic Trouble Code Chart P.14F-19.and diagnose any other DTCs that are set. If no other DTCs have been set, go to Step 2.
"Evap Lead Mon. discontinued. Retest again from the first": The EVAP monitor was 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. Go to Step 17.
STEP 3. Check for leaks in the evaporative emission system hoses A through E.
Perform a leakage test with a hand vacuum pump on each hose from hose A to hose E.
Q: Does the hoses hold vacuum?
YES: Go to Step 4.
NO: Replace any damaged hose. Go to Step 17.
STEP 4. Check the evaporative emission ventilation solenoid using scan tool MB991502. (Actuator test item 29).
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. Remove the module bracket mounting bolts and disconnect hose G from the evaporative emission ventilation solenoid.
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 MB991502 to actuator test mode for item 29: Evaporative Emission Ventilation Solenoid. While the evaporative emission ventilation solenoid is energized, operate the hand vacuum pump and confirm that solenoid holds vacuum.
6. Turn the ignition switch to the "LOCK" (OFF) position, and disconnect scan tool MB991502.
7. Disconnect the hand vacuum pump and connect hose G to the evaporative emission ventilation solenoid, and install the module bracket mounting bolts.
Q: Does the evaporative emission ventilation solenoid hold vacuum?
YES: Go to Step 5.
NO: Replace the evaporative emission ventilation solenoid. (Refer to Evaporative Emission Canister and Fuel Tank Pressure Relief Valve). Go to Step 17.
STEP 5. Pressure test the evaporative emission system lines between hose F and P.
1. Remove the module bracket mounting bolts and disconnect hose G from the evaporative emission ventilation solenoid, and plug the hose G.
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: The "Pressure test" in this procedure refers to the I/ M240 Simulation TesL The eight steps of this test are described in the manufacturer's instructions for the evaporative emission system pressure pump, Miller number 6872A.
5. Connect hose G to the evaporative emission ventilation solenoid and install the module bracket mounting bolts.
Q: Is the evaporative emission system line free of leaks?
YES: Go to Step 16.
NO: Go to Step 6.
STEP 6. Pressure test the evaporative emission system lines between hose I and P.
1. Remove the module bracket mounting bolts and disconnect hose I at the evaporative emission canister side, and plug the hose I securely.
2. Perform the evaporative emission system pressure test.
3. Disconnect the evaporative emission system pressure pump and reinstall the fuel cap.
4. Connect hose I and install the module bracket mounting bolts.
Q: Is the evaporative emission system line free of leaks?
YES: Go to Step 7.
NO: Go to Step 9.
STEP 7. Check for leaks in the evaporative emission system hoses F through H.
1. Remove the fuel tank. (Refer to Fuel Tank).
2. Perform a leakage test with a hand vacuum pump on each hose from hose F to hose H.
Q: Does the hoses hold vacuum?
YES: Go to Step 8.
NO: Replace any damaged hose and reinstall the fuel tank. (Refer to Fuel Tank). 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 them.
3. Apply vacuum with the hand vacuum pump and confirm that the canister holds vacuum.
Q: Does the evaporative emission canister hold vacuum?
YES: Go to Step 17.
NO: Replace the evaporative emission canister (Refer to Evaporative Emission Canister and Fuel Tank Pressure Relief Valve) and reinstall the fuel tank. (Refer to Fuel Tank). Go to Step 17.
STEP 9. Check for leaks in the evaporative emission system lines between hose J and K.
1. Remove the fuel filter neck protector. (Refer to Fuel Tank).
2. Disconnect hose J at the liquid separator side and connect a hand vacuum pump to the hose J.
3. Disconnect hose K at the fuel tank and plug the hose K securely.
4. Apply vacuum with the hand vacuum pump and confirm that the vacuum holds.
5. Disconnect the hand vacuum pump and connect hose K to the fuel tank.
Q: Does the evaporative emission system lines hold vacuum?
YES: Go to Step 10.
NO: Replace any damaged hose and reinstall the fuel filler neck protector. (Refer to Fuel Tank). Go to Step 17.
STEP 10. Check for leaks in the evaporative emission system hoses I, L, M, N and O.
1. Remove the fuel tank and fuel filler neck assembly. (Refer to Fuel Tank).
2. Perform a leakage test with a hand vacuum pump on each of hose I, L, M, N and O.
Q: Does the hoses hold vacuum?
YES: Go to Step 11.
NO: Replace any damaged hose, and reinstall the fuel tank and fuel filler neck assembly. (Refer to Fuel Tank). Go to Step 17.
STEP 11. Check the check valve A.
1. Check valve A is an 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 flow in one direction only?
YES: Go to Step 12.
NO: Replace check valve A, and reinstall the fuel tank and fuel filler neck assembly. (Refer to Fuel Tank). Go to Step 17.
STEP 12. Check the check valve B.
1. Check valve B is an 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 flow in one direction only?
YES: Go to Step 13.
NO: Replace check valve B, and reinstall the fuel tank and fuel filler neck assembly. (Refer to Fuel Tank). Go to Step 17.
STEP 13. Check for leaks in the evaporative emission system hose P.
Perform a leakage test with a hand vacuum pump on hose P.
Q: Does hose P hold vacuum?
YES: Go to Step 14.
NO: Replace the hose P, and reinstall the fuel tank and fuel filler neck assembly. (Refer to Fuel Tank). Go to Step 17.
STEP 14. 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, and reinstall the fuel tank and fuel filler neck assembly. (Refer to Fuel Tank). 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 differential pressure sensor installation 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 that are connected to the fuel tank.
NOTE: If these items are not securely plugged at this time, the fuel could leak from the tank.
4. Pressurize the fuel tank with the evaporative emission system pressure pump.
5. In the pressurized state, check for the leaks by applying soapy water solution to each section and look for bubbles.
Q: Is the fuel tank free of leaks?
YES Go to Step 16.
NO: Replace the fuel tank, and reinstall the fuel tank and fuel filler neck assembly. (Refer to Fuel Tank). Go to Step 17.
STEP 16. 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.
- During this test, the ECM
1. Turn the ignition switch to the "ON" position.
2. Erase the DTCs using scan tool MB991502. (Refer to Trouble Code Diagnosis - How to Read and Erase Diagnostic Trouble Codes).
3. Check that the fuel cap is securely closed. (Tighten until three clicks are heard).
4. Start the engine.
5. Select "System Test", and press the "YES" key.
6. Select "Evap Leak Mon", and press the "YES" key.
7. During the monitor, keep the accelerator pedal at the idling position.
NOTE: If the engine speed does not reach 2000 rpm during the monitor test, adjust the Speed Adjusting Screw (Refer to On-vehicle Service - Basic Idle Speed Adjustment), and adjust to the standard value.
8. Keep the engine speed and engine load within the specified range. When the monitor test starts, the "In Progress" item on the scan tool MB991502 will change from "NO" to "YES".
9. Turn the ignition switch to the "LOCK" (OFF) position, and disconnect scan tool MB991502.
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. Go to Step 17.
"Evap Leak Mon. Completed. Test Failed and DTCs Set" : Replace the ECM
"Evap Lead Mon. discontinued. Retest again from the first" : The monitor test was interrupted. Turn the ignition switch to the "LOCK" (OFF) position once and repeat evaporative emission system monitor test.
STEP 17. Perform the OBD-II drive cycle.
1. Confirm the repair by performing the appropriate drive cycle. [Refer to Trouble Code Diagnosis - OBD-III Drive Cycle (Procedure 1: Evaporative Emission Control system Leak Monitor).
2. Read the DTC.
Q: Is DTC P0456 set?
YES: Repeat the troubleshooting procedure. Go to Step 1.
NO: The procedure is complete.