EVAP Emission Control System Operation

EVAP Emission Control System Operation
The EVAP canister purge is controlled by a solenoid valve that allows the manifold vacuum to purge the canister. The Powertrain control module (PCM) 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 PCM. The output is commanded when the appropriate conditions have been met.
These conditions 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).
- A continuous purge condition with no purge commanded by the PCM will set a DTC.
- 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.