P0456

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

Circuit Description
The Evaporative (EVAP) emission 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
Calculated leak diameter is between 0.405 - 0.761 mm (0.016 - 0.030 in.).

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
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

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DTC Troubleshooting