6E1-78 DRIVEABILITY AND EMISSIONS
Evaporative Emission Canister Purge Control Solenoid Valve Check (If applicable)
ENGINE
CONTROL
MODULE
(ECM)
ENGINE FUSE
15A
IGNITION
EVAPORETIVE
EMISSION
CANISTER PURGE
SOLENOID
CONTROL DRIVER
EVAPORATIVE
EMISSION
CANISTER
PURGE CONTLOL
SOLENOID VALVE
12
N.C.
MANIFOLD
VACUUM
TO CANISTER
Circuit Description:
The EVAP canister purge is controlled by a solenoid
valve that allows the manifold vacuum to purge the
canister. The engine control module (ECM) supplies a
ground to energize the solenoid valve (purge on). The
EVAP purge solenoid control is pulse- width
modulated (PWM) (turned on and off several times a
second). The duty cycle (pulse width) is determined by
engine operating conditions including load, throttle
position, coolant temperature and ambient
temperature. The duty cycle is calculated by the ECM.
The output is commanded when the appropriate
conditions have been met. These condi-tions are:
• The engine is fully warmed up.
• The engine has been running for a specified time.
• The IAT reading is above 10°C (50°F).
The EVAP purge vacuum switch is a normally closed
switch positioned in the purge line between the
canister and the EVAP purge control solenoid valve.
A continuous purge condition with no purge
commanded by the ECM will set a DTC62.
Poor idle, stalling and poor driveability can be caused
by:
• A malfunctioning purge solenoid.
• A damaged canister.
• Hoses that are split, cracked, or not connected
properly.
Test Description:
Numbers below refer to circled numbers on the
diagnostic chart.
1. Check to see if the solenoid is opened or closed.
The solenoid is normally de-energized in this step,
so it should be closed.
2. Check to determine if solenoid was open due to
electrical CKT problem or defective solenoid.
3. Completes functional check by grounding test
terminal. This should normally energize the
solenoid opening the valve which should allow the
vacuum to drop (purge “ON“).
Diagnostic Aids:
Make a visual check of vacuum hose(s). Check
throttle body for possible cracked, or plugged vacuum
block.
Malfunction indicator lamp for possible mechanical
problem.
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