P0456

DTC P0456 EVAP Very Small Leak




Circuit Description
The evaporative system includes the following components:
- Fuel tank
- EVAP canister vent solenoid
- Fuel tank pressure sensor
- Vapor lines
- Fuel cap
- Evaporative emissions canister
- Purge lines
- EVAP canister purge solenoid

The evaporative leak detection diagnostic strategy is based on applying vacuum to the EVAP system and monitoring vacuum decay. The powertrain Control module (PCM) monitors vacuum level via the fuel tank pressure sensor input At an appropriate time, the EVAP canister purge solenoid and the EVAP canister vent solenoid are turned "ON," allowing engine vacuum to draw a very small on the entire evaporative emissions system. After the desired vacuum level has been achieved, the EVAP canister purge solenoid is turned "OFF", sealing the system. A leak is detected by monitoring for a decrease in vacuum level over a given time period, all other variables remaining constant.

A very small leak in the system will cause DTC P0456 to be set.

Conditions for setting the DTC
- No MAP DTC's set.
- No TPS DTC's set.
- No IAT DTC's set.
- No ECT DTC's set.
- No tank pressure sensor DTC's set.
- Baro is more than 70 KPa.
- A vacuum decay condition, indicating a very small leak, is detected during the diagnostic test.

Action Taken When the DTC Sets
- The PCM will illuminate the malfunction indicator lamp (MIL) after the second consecutive trip in which the fault is detected.
- The PCM will store condition which were present when the DTC was set as Freeze Frame and in the Failure Records data.

Warm up cycles have occurred without a fault.

Conditions for Clearing the MIL/DTC
- The PCM will turn the MIL "OFF" on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present.
- A history DTC P0456 will clear after 40 consecutive trip cycle during which the warm up cycles have occurred without a fault.
- DTC P0456 can be cleared using the Tech 2 "Clear Info" function or by disconnecting the PCM battery feed.

Diagnostic Aids
Check for the following conditions:
- Cracked or punctured EVAP canister.
- Damaged source vacuum line, EVAP purge line, EVAP vent hose or fuel tank vapor line to wire connection.
- Poor connection at PCM - Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
- Damaged harness - Inspect the wiring harness to the EVAP canister purge solenoid and the fuel tank pressure sensor for an intermittent open or short circuit.

Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs.

This may assist in diagnosing the condition.

Steps 1 - 3:

Steps 4 - 7:

Test Description