The computer notices the canister when the car engine is tested and it is found empty when it notices a leaner complaint of all the vapors are used up and it recommences usual fuel distribution. Some car producers then close the vent solenoid but leave the purgative solenoid open. That generates a vacuum through the whole fuel storage system. Once the right vacuum is touched, it locked the purge solenoid and delays to see if the vacuum holds. You need to check the list and in the list, you will get Ambient Air Temperature Sensor Circuit Low, Cold Start Injector 1 Malfunction and Shift Solenoid E Performance or Stuck Off.