System and method for evaporative emissions detection
Methods and systems are provided for conducting an evaporative emissions test on a fuel system in a vehicle. In one example, in response to a determination, based on the prevailing vehicle and ambient thermal conditions, that altering vehicle height may increase pressure or vacuum build during a pressure or vacuum build phase of an engine off natural vacuum test, employing the vehicle's active suspension to make said height adjustments. In this way the accuracy of engine off natural vacuum testing can be improved, and the conditions under which such testing can be efficaciously conducted increased.
1. A method, comprising:
adjusting a vehicle suspension height responsive to a fuel system diagnostic test, wherein the adjusting includes lowering the vehicle suspension height responsive to a pressure build-up phase and raising the vehicle suspension height responsive to a vacuum build-up phase of the fuel system diagnostic test relative to a default vehicle suspension height based on a driver requested drive mode.
2. The method of claim 1 , wherein the vehicle suspension height is further adjusted responsive to estimated ground temperature.
3. The method of claim 2 , wherein the vehicle suspension height is lowered further from the default vehicle suspension height during the pressure build-up phase of the diagnostic test as the estimated ground temperature increases, and wherein the vehicle suspension height is raised further from the default vehicle suspension height during the vacuum build-up phase of the diagnostic test as the estimated ground temperature increases.
4. The method of claim 1 , wherein the fuel system diagnostic test is a fuel evaporative system integrity test including the pressure build-up phase followed by the vacuum build-up phase, the fuel system isolated during each of the pressure build-up phase and the vacuum build-up phase, and the fuel system vented in between the pressure build-up phase and the vacuum build-up phase.
5. The method of claim 1 , further comprising resuming the default vehicle suspension height upon completion of the fuel system diagnostic test.