Acronyms and Abbreviations QSC8.3 and QSL9 Page i-10 Section i - Introduction SCA Supplemental Coolant Additive SCR Selective Catalytic Reduction STC Step Timing Control SID Subsystem Identification Descriptions TDC Top Dead Center VDC Volts of Direct Current VGT Variable Geometry Turbocharger VS Variable Speed VSS Vehicle Speed Sensor