Fuel tank isolation valve controls and diagnostics

A method for controlling carbon emissions of an evaporative emissions system of a vehicle having an engine, a fuel tank configured to provide fuel for the engine, and a carbon canister configured to capture hydrocarbon emissions from the fuel tank, the method comprising:

• obtaining sensor data via a plurality of sensors for the evaporative emissions system;
• and
• selectively controlling a first valve disposed between the carbon canister and the engine and a second valve disposed between the fuel tank and the carbon canister, via one or more processors, to thereby control hydrocarbon emissions from the carbon canister and maintain performance of the engine, using the sensor data;
• wherein the method further comprises:
• determining, via the one or more processors using the sensor data, whether conditions are appropriate for aggressive purging of the carbon canister;
• when it is determined that the conditions are appropriate for the aggressive purging, commanding, via the one or more processors, the first valve to be biased open and the second valve to be closed while providing instructions for the aggressive purging at a first flow rate;
• and
• when it is determined that the conditions are not appropriate for the aggressive purging, commanding, via the one or more processors, the second valve to be open while providing instructions for conservative purging at a second flow rate that is less than the first flow rate.

A control system for controlling carbon emissions of an evaporative emissions system of a vehicle having an engine, a fuel tank configured to provide fuel for the engine, and a carbon canister configured to capture hydrocarbon emissions from the fuel tank, the control system comprising:

• a plurality of sensors configured to obtain sensor data for the evaporative emissions system;
• and
• one or more processors that are coupled to the plurality of sensors and that are configured to at least facilitate selectively controlling a first valve disposed between the carbon canister and the engine and a second valve disposed between the fuel tank and the carbon canister, to thereby control hydrocarbon emissions from the carbon canister and maintain performance of the engine, using the sensor data;
• wherein the one or more processors are further configured to at least facilitate:
• determining, using the sensor data, whether conditions are appropriate for aggressive purging of the carbon canister;
• when it is determined that the conditions are appropriate for the aggressive purging, commanding the first valve to be biased open and the second valve to be closed while providing instructions for the aggressive purging at a first flow rate;
• and
• when it is determined that the conditions are not appropriate for the aggressive purging, commanding the second valve to be open while providing instructions for conservative purging at a second flow rate that is less than the first flow rate.