P0456

DTC P0456

CIRCUIT DESCRIPTION
The EVAP small leak test applies vacuum to the EVAP system and monitors vacuum decay. The control module monitors the fuel tank pressure sensor signal to determine the vacuum decay rate. At an appropriate time, the EVAP canister purge valve and the EVAP vent valve are turned ON. This allows the engine to draw vacuum on the EVAP system. After the desired vacuum level has been achieved, the EVAP purge valve is turned OFF, sealing the system. A leak is detected by monitoring for a decrease in the vacuum level during a given time period. If the system detects a leak larger than a calibrated amount, DTC P0456 will set.

DTC DESCRIPTORS
This diagnostic procedure supports the following DTC:
DTC P0456 Evaporative Emissions (EVAP) Very Small Leak Detected

CONDITIONS FOR RUNNING THE DTC
- Before the engine control module (ECM) can report DTC P0456 failed, DTC P0441 must run and pass.
- DTCs P0106, P0107, P0108, P112, P0113, P0117, P0118, P0122, P0123, P0131, P0132, P0133, P0134, P0137, P0138, P0140, P0141, P0201, P0202, P0203, P0204 P0402, P0404, P0405, P0406, P0443, P0452, P0453, P0462, P0463, P0488, P0502, P2195, and P2196 are not set.
- The barometric pressure (BARO) is more than 72 kPa.
- The engine coolant temperature (ECT) at start-up is more than minus 5°C (23°F).
- The intake air temperature (IAT) at start-up is less than 40°C (104°F).
- The engine is OFF for more than 6 hours or the following conditions must be met:
- The start-up IAT minus start-up ECT are within 12°C (22°F).
- The start-up ECT minus startup IAT is within 50°C (90°F).
- The start-up IAT minus IAT are within 3°C (5°F).
- The ignition 1 voltage is between 11-16 volts.
- The fuel level is between 1/4 and 3/4.
- Purge start time is less than 360 seconds.
- Engine Run Time is more than 1 second and less than 120 seconds.
- DTC P0456 runs once an ignition cycle when the above conditions are met.

CONDITIONS FOR SETTING THE DTC
The EVAP system can achieve vacuum but a vacuum decay is detected during the diagnostic test.

ACTION TAKEN WHEN THE DTC SETS
- The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
- The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
- The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
- A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
- Clear the MIL and the DTC with a scan tool.

DIAGNOSTIC AIDS
To help locate intermittent leaks, use the J 41413-200 Evaporative Emissions System Tester (EEST) to introduce smoke into the EVAP system. Move all EVAP components while observing smoke with the J 41413-SPT High Intensity White Light. Introducing smoke in 15 second intervals will allow less pressure into the EVAP system. When the system is less pressurized, the smoke will sometimes escape in a more condensed manner.

TEST DESCRIPTION

Steps 1-2:

Step 3:

Step 4:

Steps 5-6:

The numbers below refer to the step numbers on the diagnostic table.
6. This step verifies that repairs are complete and that other conditions are not present.