Secondary Air Injection

Secondary air injection is required to pre-heat the catalytic converters for OBD II compliance. The DME ME7.2 control unit controls the vacuum vent valve and the secondary air injection pump relay separately but simultaneously. The secondary air pump operates at a start temperature of between 50-104°F (10-40°C). It continues to operate for a maximum of 2 minutes at idle speed. ME 7.2 contributes an additional correction factor for secondary air "on" time with the additional input from the integral ambient barometric pressure sensor. This sensor provides a base value to calculate the air mass being injected into the exhaust system. This helps to "fine tune" the secondary air injection "on" time, optimizing the necessary air flow into the exhaust system which reduces the time for catalytic converter light-off.