P0456

DTC P0456 Evaporative Emission Control System Small Leak Detected (0.5 mm)

Circuit Description

The evaporative emission (EVAP) system includes the following components:
- Fuel tank
- EVAP vent solenoid
- Fuel tank pressure sensor
- Fuel pipes and hoses
- Fuel vapor lines
- Fuel cap
- EVAP canister
- Purge lines
- EVAP canister purge valve
- EVAP service port
The evaporative emission system is checked by applying vacuum to the EVAP system and monitoring for a vacuum decay. The engine control module (ECM) monitors the vacuum level through the fuel tank pressure sensor signal.
At the appropriate time, the EVAP canister purge valve and the EVAP vent solenoid are turned ON, allowing the engine to draw a small vacuum on the entire evaporative emission system. After the desired vacuum level has been achieved, the EVAP canister purge valve is turned OFF, sealing the system. A leak is detected by monitoring for a decrease in the vacuum level over a given time period, when all other variables remain constant. A small leak in the system will cause DTC P0456 to be set.

Conditions for Setting the DTC

- Engine run time is greater than 590 seconds.
- Vehicle Speed is less than 3.7 mph (6 km/h).
- Leak diameter is greater than 0.421 mm.
- Coolant temperature is greater than 70 °C (158 °F).
- Air temperature at start is greater than -9.75 °C (14.4 °F).
- Estimated altitude is less than 2600 m.
- Engine is running.
- Fuel tank pressure is between -0.8 kpa and 0.3 kpa.

Action Taken When the DTC Sets

- The Malfunction Indicator Lamp (MIL) will illuminate.
- The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.
- A history DTC is stored.

Conditions for Clearing the MIL/DTC

- The MIL will turn off at the end of 3 consecutive ignition cycles in which the diagnostic runs without a fault.
- A history DTC will clear after 40 consecutive warm-up cycles without a fault.
- DTC(s) can be cleared by using the scan tool.

Diagnostic Aids

Although this DTC is considered a type A diagnostic it acts like a type B diagnostic under certain conditions. Whenever this diagnostic reports the system has passed, or if the battery is disconnected, the diagnostic must fail twice before setting a DTC. The initial failure is not reported to the diagnostic executive or displayed on a scan tool. A passing system always reports to the diagnostic executive immediately.

Check for the following conditions:

1. Missing or damaged O-rings at fuel vapor and EVAP emission purge line canister fittings.
2. Cracked or punctured EVAP emission canister.
3. Damaged source vacuum line, EVAP emission purge line, EVAP emission vent hose or fuel tank vapor line.
4. Poor connection at ECM. Inspect harness connectors for the following conditions:
- Backed-out terminals
- Improper mating
- Broken locks
- Improperly formed
- Damaged terminals
- Poor terminals to wire connection
- Physical damage to the wiring harness
5. Missing or damaged O-rings at fuel vapor and EVAP emission purge line canister fittings.

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DTC P0456 - Evaporative Emission Control System Small Leak Detected (0.5 mm)