Secondary Air Injection

Secondary air injections required to pre-heat the catalytic converters for OBD II compliance. The system consists of the same components as previous systems with V8 specific locations.

Fig 1: Identifying Vacuum Vent Valve And Vacuum Control To Non Return Valve

Courtesy of BMW OF NORTH AMERICA, INC.

Fig 2: Identifying Secondary Air Injection Components

Courtesy of BMW OF NORTH AMERICA, INC.

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 10°C and 40°C. It continues to operate for a max. 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 to catalytic converter light-off.

Fig 3: Identifying DME ME 7.2 Control Unit Circuit Diagram

Courtesy of BMW OF NORTH AMERICA, INC.