Canister Purge Solenoid: Testing and Inspection

FUNCTIONAL CHECK CANISTER PURGE SOLENOID

Monitoring the canister purge solenoid

The diagnosis is used for the functional test of the CP solenoid. There for the CPS is diagnosed via its effects on the engine.
The functional check of the CPS consists of 2 steps:
- Step 1: based on the ACF load degree
- Step 2: based on
- the deviation of lambda-controller
- TQ deviations
- the deviation of the reduced area at the throttle

If the CPS has been detected to be OK within a step or as not OK after a step then the function is exited irreversibly until the next engine start.
The steps 1 and 2 are processed successively, i.e. the next step may only be performed if the proceeding one has not been detected as OK. The only exception is step 1. Step 1 may also be performed parallel to step 2.
After step 1 has been processed once and CPS has not been detected as OK then (if enable conditions are fulfilled) it is proceeded with step 2 and at the same time calculation of step 1 is started again. Calculation of step 1 is done until CPS is detected as OK within one of the steps (1 or 2) or until CPS is detected as definitely not OK by the end of step 2.
If the CPS is detected to be not OK after all 2 steps have been passed (end of step 2), then the error is set.
The complete diagnosis "functional check CPS" is performed only once per driving cycle
The first check of the CPS is based on the ACF-load degree. The "Canister Load diagnosis" is calculated permanently until the complete check CPS is finished. The canister load has to be over threshold for defined time to detect the system as OK.
During the next check, the CPS is evaluated based on the change of lambda controller, the change of engine torque and the change of the reduced area at the throttle. To this effect, the CPS is opened for a short time and all values (Lambda controller, Engine torque, reduced area at the throttle) are monitored for a certain period.
After this check has been enabled for the first time, it is requested during each idle speed phase. This is repeated as long as a result has been reached. This check is not bound to one IS phase, but can be distributed to several IS phases.
If the CPS is detected to be not OK after one check, the error is set.

Flow chart: Functional check CPS