P0456

DTC P0456 EVAPORATIVE EMISSION CONTROL SYSTEM LEAK DETECTED (VERY SMALL LEAK)

CIRCUIT DESCRIPTION

DTC Detecting Condition:

The evaporative emissions (EVAP) system is equipped to reduce EVAP in the fuel tank.

The EVAP system consists as the follows:
- EVAP canister: Stores EVAP in the fuel tank.
- Fuel tank pressure (FTP) sensor: Measures the FTP.
- EVAP VSV (EVAP canister purge valve): Purges EVAP in the EVAP canister into the intake manifold when it is opened.
- CCV (EVAP canister vent valve): Introduces atmosphere to the EVAP canister when it opens.
The CCV opens under the normal condition.
- Bypass VSV (EVAP canister pressure switching valve): Connect the fuel tank and EVAP canister

MONITOR DESCRIPTION

Monitor Strategy:

Typical Enabling Conditions:

Typical Malfunction Thresholds:

Monitor Result:

The ECM monitors evaporative emissions (EVAP) leak and the components on the EVAP system using a continuous test; EVAP System Test. The EVAP System Test is done according to the following procedures:
a. The ECM starts the EVAP System Test when the following conditions are met.
- The engine coolant temperature (ECT) and the intake air temperature (IAT) is 10 to 35 °C (50 to 95°F) when the engine was started.
- The difference of the ECT and IAT is -7 to 11 °C (-12.6 to 20 °F) when the engine was started.
- Fuel tank pressure (FTP) is stabilized.

b. The ECM measures the FTP rising.
c. The ECM closes the canister closed valve (CCV) to shut off atmosphere and opens the bypass VSV to connect the EVAP canister and the fuel tank. And the ECM opens the EVAP VSV to apply the intake manifold pressure into the EVAP canister and the fuel tank ("negative pressure introduction").
d. The ECM closes the EVAP VSV to stop "negative pressure introduction". The EVAP system is sealed.
If the FTP does not drop during "negative pressure introduction", the ECM interprets this as EVAP VSV "stuck close". The ECM illuminates MIL (2 trip detection logic) and sets DTC P0441.
e. The ECM measures the FTP increase for 5 sec ("EVAP leak check").
If the FTP increase is larger than the specified value, the ECM interprets this as EVAP 0.02 inch leak. The ECM illuminates MIL (2 trip detection logic) and sets DTC P0456.
If the FTP increase is larger than EVAP 0.02 inch leak, the ECM interprets this as EVAP 0.04 inch leak. The ECM illuminates MIL (2 trip detection logic) and sets DTC P0442.
If the FTP increase is larger than EVAP 0.04 inch leak, the ECM interprets this as EVAP gross leak. The ECM illuminates MIL (2 trip detection logic) and sets DTC P0455.
f. The ECM opens the CCV to check the CCV operation.
If the FTP increase is smaller than the specified value, the ECM interprets this as CCV "stuck close". The ECM illuminates MIL (2 trip detection logic) and sets DTC P0446.
g. The ECM closes the bypass VSV to check the bypass VSV operation.
If the FTP increase is larger than the specified value, the ECM interprets this as bypass VSV malfunction.
The ECM illuminates MIL (2 trip detection logic) and sets DTC P2418.
If the FTP is less than the specified value, the ECM interprets this as EVAP VSV "stuck open" or CCV "stuck closed". The ECM illuminates MIL (2 trip detection logic) and sets DTCs P0441 and P0446.

Wiring Diagram:

CONFIRMATION READINESS TEST

First Trip Procedure
a. The vehicle must be cold, and the ambient temperature must be between 10 to 35 °C (50 to 95 °F).
b. The IAT and ECT have almost the same value.

c. Clear the DTCs.
Then, readiness tests will show INCMPL (incomplete).

d. Drive the vehicle according to the LA# 4 driving cycle. Note the state of the Readiness Tests. They will change to COMPL as the EVAP evaluation monitors operate and if the system passes. This procedure may take 20 minutes or more.

NOTE: Do not shut off the engine - the results will be invalid.

Pass Condition - No Problem Found by the ECM

If the EVAP evaluation monitor shows COMPL, go to the Non-Continuous Test screen.

NOTE: Do not shut off the engine - the results will be invalid.

To get there, go to Advanced OBD II, Onboard Tests, Non-continuous Tests.

If all of the tests in the time $02 category Tests show Pass, the EVAP evaluation monitor has operated and no problem was detected.

Fail Condition - Problem Detected by the ECM

If the EVAP evaluation monitor shows INCMPL, go to the Non-Continuous Test screen.

1. If all Tests show Pass, the following may have occurred.
- The EVAP evaluation monitor did not operate.
- The EVAP evaluation monitor did not finish.
- The ECM withheld judgement.

2. If one or more of the tests in the time $02 category show Fail, the EVAP evaluation monitor did operate and the ECM detected a problem.

3. Go to Continuous Tests screen. This is the only place DTC's are listed for the first trip.

NOTE: The DTC listed may not be valid. Second trip is needed to confirm the DTC.

Second Trip Procedure
a. Vehicle must be cold, ambient temperature between 10 to 35 °C (50 to 95 °F).

b. Go to Readiness Tests screen.
c. Drive the vehicle according to LA# 4 drive cycle. Note the state of EVAP evaluation monitor. This procedure may take approximately 20 minutes or more.

NOTE: Do not shut off the engine - the results will be invalid.

d. If Readiness Tests changes to COMPL, the EVAP evaluation monitor has operated. Check for any stored DTC's.
- If a DTC has stored, the problem has been detected and confirmed by the ECM.
- If no DTC was found, the EVAP monitor operated but no problem was detected.

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INSPECTION PROCEDURE

HINT:
- If DTC P0441 (EVAP VSV), P0446, P2418 (CCV or bypass VSV), P0451, P0452 or P0453 (FTP sensor) is output with DTC P0442, P0455 or P0456, first troubleshoot DTC P0441, P0446, P2418, P0451, P0452 or P0453. If no malfunction is detected, troubleshoot DTC P0442 or P0456 next.
- Ask the customer whether, after the MIL came on, the customer found the fuel tank cap was loose and tightened it. Also ask the customer whether the fuel tank cap was loose when refuelling. If the fuel tank cap was loose, it was the cause of the DTC. If the fuel tank cap was not loose or if the customer was not sure if it was loose, troubleshoot according to the following procedure.
- Read freeze frame data using the hand-held tester. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction.
- When the ENGINE RUN TIME in the freeze frame data is less than 200 seconds, carefully check the FTP sensor.