| Description and Operation Exhaust Gas Recirculation ( EGR) system The EGR valve is vacuum-actuated. The vacuum is created by a vacuum pump on the camshaft. The EGR solenoid is activated by the PCM and controls the vacuum for actuation of the EGR valve. The PCM determines the EGR valve operating cycles and, therefore, the recirculated exhaust gas volume as a function of the intake air volume. Vacuum pump The vacuum pump is flange-mounted to the camshaft housing on the flywheel side of the engine. The vacuum pump is directly driven by the camshaft. The vacuum created in this way is used for actuating the EGR valve and the turbocharger wastegate as well as for brake servo assistance. Catalytic converter The engine is equipped with an oxidising catalytic converter to ensure that the emissions standards for diesel engines are met. In order to improve its efficiency when cold, the oxidising catalytic converter is located near the engine and is connected directly to the turbocharger. | 
