Diagnostic method for a refueling event detection system

1. A method for diagnosing the performance of a refueling event detection system for a vehicle equipped with an engine, said method comprising:

determining a fuel change amount based on a difference of an indicated fuel amount and a previously indicated fuel amount;

determining a consumed amount of fuel consumed by the engine since a prior refueling event was detected; and

diagnosing the performance of the refueling event detection system based on the consumed amount and the fuel change amount, wherein the step of diagnosing includes

determining an indicated refueling amount based on the fuel change amount if a refueling event is detected;

determining a refueling ratio based on the consumed amount and the indicated refueling amount; and

determining a blended ratio based on the refueling ratio and a historic ratio.

2. The method according to claim 1 , wherein the step of diagnosing further includes determining that a false detection of the refueling event by the refueling event detection system has occurred if the blended ratio is less than a low threshold.

3. The method according to claim 1 , wherein the step of diagnosing further includes determining that the refueling event has not been detected by the refueling event detection system if the blended ratio is greater than a high threshold.

4. The method according to claim 1 , wherein the step of diagnosing includes subtracting a compensation amount from an indicated refueling amount if the indicated fuel amount is greater than a previous maximum fuel amount.

5. The method according to claim 4 , wherein the compensation amount is determined based on a difference of the indicated fuel amount and the previous maximum fuel amount.

6. The method according to claim 1 , wherein the step of diagnosing includes determining a refueling ratio based on a default value if a refueling event is not detected and the consumed amount is greater than a consumption threshold.