The 535-6924 Genuine CAT DEF Control Manifold is a diesel exhaust fluid manifold/head unit used in select Caterpillar DEF/SCR aftertreatment systems. CAT identifies this part as a Diesel Exhaust Fluid (DEF) Control Manifold, 442 mm / 17.4 in long, with a 4-pin DT connector. This component supports DEF system operation by managing DEF pickup, routing, and system monitoring functions required for SCR emissions control. It is used on select Caterpillar equipment and engine applications, including listed C3.6 and C4.4 industrial engine platforms. Correct fitment is important because DEF manifolds can vary by tank design, harness connection, emissions configuration, and machine serial number. Verify fitment by CAT model, serial number, original part number, and CAT SIS/parts information before ordering.