If there is an internal leak in the valve, diagnostic trouble code P0441 will be generated.
NOTE:
The purging adaptation can cause problems when fault diagnosing the fuel system because the closed loop can fluctuate around 0% in spite of major faults such as air leaks. If a light emitting diode is connected instead of the canister purge valve and the purging adaptation read with the diagnostic tool it will, when the purging is active, show the entire fuel fault on condition that the multiplicative and additive adaptation is first zeroed.