Exhaust Gas Recirculation (EGR)
WARNING: This page is about a different car, the 1992 Mercedes-Benz 400E. However, it is still accessible from the selected car via links, so may be relevant.
EGR system is controlled by LH control unit through EGR switchover valve. To reduce emissions, approximately 10-15 percent of exhaust gas is recirculated from the exhaust manifold. The recirculated exhaust gas enters air intake after hot-wire air mass sensor. This causes not effect on hot-wire air mass sensor. The LH control unit activates EGR switchover valve when coolant temperature is more than 149°F (65°C) and engine is not at idle or full load.