Workshop Manual

6E–341
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0456 EVAP Very Small Leak
060R200050
Circuit Description
The evaporative system includes the following
components:
B Fuel tank
B EVAP canister vent solenoid
B Fuel tank (vapor) pressure sensor
B Vapor lines
B Fuel cap
B Evaporative emissions canister
B Purge lines
B 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 look 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
B No MAP DTC’s set.
B No TPS DTC’s set.
B No IAT DTC’s set.
B No ECT DTC’s set.
B No tank pressure sensor DTC’s set.
B Baro is more than 70KPa.
B Fuel level is between 40% and 80%.
B Throttle angle is less than 3%.
B Engine speed is less than 1200 RPM.
B Vehicle speed is less than 5 mph (8 km/h).
B A vacuum decay condition, indicating a very small leak,
is detected during the diagnostic test.
Action Taken When the DTC Sets
B The PCM will illuminate the malfunction indicator lamp
(MIL) after the second consecutive trip in which the
fault is detected.
B 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
B 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.