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FUEL CAP OFF DETECTION METHOD AFTER REFUELING EVENT

IP.com Disclosure Number: IPCOM000242228D
Publication Date: 2015-Jun-26
Document File: 1 page(s) / 223K

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The IP.com Prior Art Database

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FUEL CAP OFF DETECTION METHOD AFTER REFUELING EVENT

Vehicles sold in the North America market are required to perform Evap leak detection as part of OBDII requirements. TheEvap leak diagnostic for the 0.04" leak uses engine vacuum to evacuate the entire Evap system to a target vacuum (typically -8 InH2O) during vehicle cruising conditions. The Canister Vent Valve (CVV) is closed to seal the system, then vacuum from the intake manifold is introduced into the Evap system. If a target vacuum is not reached, SAE DTC P0455 is used to indicate a "gross" leak.

Many entry criteria are required prior to running the Evap leak test. Some criteria are mandated by CARB, such as fuel level

15%, ambient temperature

40 degF and altitude <8500 feet. Other entry criteria include a warm engine, hot catalyst, closed loop fuel control, good combustion stability, no MILs, etc… The reason is that when the Canister Purge Valve (CPV) opens, there is no knowledge of how much vapor is going to enter the engine. Too much vapor can stall the engine. Hence, the purge command is ramped slowly up to ensure that there are no big disturbances to the Air/Fuel ratio. After a refuel event, a special leak detection test executes to make sure a driver does not forget to put on the gas cap; or in a capless fuel system, the test determines whether contaminants reside on the capless seal to cause a leak. If a gross leak is detected after a refueling event, DTC P0457 sets. While the special gross leak test usually executes within minutes o...